I'll second the recommendation to go to HR. BM's friend can hold whatever opinion of you that she/he wants, but as soon as they spread it at work (with the intention of harming your career and/or credibility), it goes too far.

There is a reason that the general advice on here is to not start claiming step kids as your own or let them call you mom. Women in particular get very teritorial about someone else claiming to be their children's mother - and the worse they are at mothering the louder their protestations will be due to thier own insecurities. Avoiding the word mom can avoid a lot of drama.

Obviously it is a personal decision for each family though.  

Personally I chose to see step-mom as a neutral term that lets people know that I am married to my step-daughter's dad. If someone asks if I have kids, I reply that I have a step daughter. 

It doesn't say anything about how much I love my step daughter, it doesn't say anything about what I do or do not do for her, it doesn't say anything about how my step daughter thinks about me. It just describes our legal (?) relationship.

People that get to know me and my step daughter will get to know those things for themselves. 

Not being "mom" is not an insult, it is a description - you are not legally or biologically these children's mother. If you can start to think of it as such when outsiders say this to you then you might be able to let go of some of your anger.

It sounds like BM is not going to go away or quiet down anytime soon, so I would work on disenaging from her as much as possible and finding your own self confidence in your role as step mother that when people point out facts to you it doesn't feel as upsetting.

You don't need to explain or rationalize to anyone why you call the children "yours" or why they call you "mom' - just accept that those that know you will understand and accept and those that don't are pointing out facts as they see it. 

I like to joke that SD9 adopted me when she was four. She began calling me mommy almost immediately and still does to this day. Her BM has been out of the picture since she was in diapers. You said, "The only crime that I am guilty of is being good to kids that she disregarded." I understand that completely. I also see the other side of it. Yes, I'm the one doing the work. Yes, I'm the one raising her. Yes, I'm here and BM doesn't want to be. However, she isn't mine. Her BM sees her a few times per year for short visits, and although she is a scumbag, she is the real mom (and her DNA shines through more and more the older SD gets, unfortunately). There is a chance that SD will grow up and form a relationship with BM one day. The likelihood of her growing up and hurting my feelings is high. It's a risk that I honestly wish I didn't take when I became the "substitute mommy." That bothers me more than what others think of the situation. People are always going to find something wrong with what you're doing, even if it's kind and good. Hang in there.

Ehhhh it's choppy waters.  You can say it's only a name but it's far more than that.  Otherwise, BM wouldn't have her knickers in a twist.  Regardless of how vile and useless a BM might be, she is still the "mom".  Biologically, legally, all the -ly's.  That's why she loses her marbles.  Is she unfit and worthless and nuts?  Yes.  Is it fair?  Absolutely not.  However - did you give birth to them? No.  Legally would you have any rights? No.

Back when my SS17 was 10, he wanted to call me mum (I live in England).  I was doing all of the mum things - taking him to school, doing his laundry, tucking him into bed at night.  But I'm not the mum so I explained to him that even though your mummy lives far away, she will always and forever be your mummy.  So he could call me Stepmum or Cookies...he calls me by my first name.  If you read my blogs, his BM2 is a psychopathic P.O.S.....but she is STILL his mum.

So I commend you for doing all the things for those girls.  It's not their fault their BM is a loser nutjob.  Letting skids call the stepparent by a bio parent label will always cause problems though.  Perhaps you could compromise on a loving nickname? 

It is just one of the cardinal sins.  Along with cutting their hair.  Big no-no.

Good luck OP, you're doing great

I really feel for you.

No doubt in my eyes you are their mother. Of course in law giving birth to a child makes you a mother but in reality it's a lot more than that.

You should definitely talk to your HR department it is not acceptable that you be put into this position at your place of work, there is a very clear attempt to damage your reputation & credibility and therefore not acceptable in the workplace.

As for the children's motherI view it very differently to the others positing here. she gave birth to them. You are their mum. Your the one they likely want when they are sick, tired, grumpy, upset, happy, proud of their achievements - that is a mother. She gave birth to them and then by the sounds of it dumped them, gave up on them and so whilst she brought them into the world that is all she has done, I actually think it doesn't matter what she wants to be called or you really for that matter - the people who matter in this scenerio is them. So if you to them are their mother that's who you are. She had a choice and she decided not to be there for them.

 i really hope you get the work stuff sorted as apart from her constantly looming about in the background it does sound like you have a lovely family - those children are lucky to have you.

I answered the job question last night, but I'll discuss the naming convention part of your post now, post-birthday gluttony.

I'm almost always on the fence when it comes to using the terms "mom" and "dad" for stepparents. I watched BM push my SSs to call their former SF "Daddy" even though my DH was active in their life. Not as active as he should be, but between BM trying (unsuccessfully) to alienate the kids from him and neither BM or her now-XH working, DH's job was to keep funneling money to BM to raise the boys since the courts didn't seem him worthy of custody even though he had income at the time of their divorce.

It KILLED him to watch his sons call that man "Daddy" and made him feel like a worthless father even though he was the only reason his kids had shelter, clothes, medicine, toys, etc. And XSF was a useless piece of trash who stole from the boys' piggy banks and didn't even pay his own CS to his own kid. YSS really loved his SF, and it CRUSHED him when he left the first time. BM didn't bother to care about how her kicking him out and bringing him back (at least 4 times while I have been around) hurt the kids. Her goal was to hurt DH, and she did it.

On the flip side, my SBro calls my mom "Mom", as does his wife. My mom is "Grandma" to their daughter. My SBro is my brother, his wife is my SIL, and their daughter is my niece. My mom has acted more like a mother to him and treated him as her own from the start, even though he and I were both teenagers when they started dating and got married. My mom earned the title of "Mom" from him because his own mother is a/an <insert favorite insult here>. His BM disowned him in a text on Christmas because he refused to put up with her toxic games. So, now my mom and SF are just "mom and dad".

And yet on another side, despite being raised "like his own" and me having no major qualms with my SF (and actually loving him and probably being closer to him than my own dad), I feel weird if I call him "dad". Sometimes I'll do it in conversation with my SBro and SIL to keep things simple, but my relationship with my dad still exists. Also, there is complications thrown in with my biosibs, where I was raised primarily by my mom and SF, but custody switched when they moved away, so my younger brother and sister were raised by my dad. There is this weird split of which of us is close to which parenting unit, and the older I get and the longer I'm a SP, the less and less that I like to co-mingle terms. Calling my SF "dad" makes him feel good, and in a lot of ways, he deserves the honorific. But, my dad is my dad, and despite him and I having a rough go at a relationship, he has been more of a father to my siblings than my mother has been a mother.

I'm not saying any of this to persuade you to change back to being SM. I'm trying to give you a picture that, emotionally - even for the kids - it's not as simple as just calling a SP "mom" or "dad". My SBro went to therapy and mourned the loss of his mother. It hurt him *deeply* when he lost her, even though she's a pretty terrible human being (long story for a different day). My YSS mourned the loss of his SF, and it caused both mental and physical symptoms. My DH STILL feels worthless in part due to "losing" his title to someone that would be homeless right now, in his 40s, if his mommy amdd daddy didn't take him in after BM gave him the boot.

This is a hotly debated topic, and one that usually ends with folks saying "don't become Mom/Dad" because there is a lot of room for pain and manipulation there. And since we're a venting/advice board for SPs, our advice is going to be skewed to protect the hearts, bodies, and mind of SPs over a lot of those other things. And protecting a SP isn't the same as saving a marriage or relationships with SKs.

So, do I think you've earned the title? Sure. The kids have deemed you worthy. I'm not sure about what your DH has done to help facilitate a relationship with BM, but if BM is truly the one who has given up visitation and been unreliable, and your DH has encouraged both her and the kids to have a better relationship but BM has been the one to rebuff those attempts, then BM can't blame you two for what has happened between her and her children.

HOWEVER, guilt is a strong emotion, and drugs will make you do and say crazy things. Unfortunately, BM lives in your community, and if she feels slighted, she's going to take it out on the easiest person to scapegoat - you. Taking on the title of "Mom" opens you up to criticism and attack from both BM and her cronies. If she finds that this attack against your credibility doesn't work, then she's going to up the ante. Be prepared. It wouldn't surprise me if she called CPS on you to make you look bad.

SO ADDITIONAL ADVICE RELATED TO WORK AND HOME: Definitely take this to HR so that you can start showing a paper trail of BM attacking your character through other and through work. Keep a copy of the report you file and any communications you have with HR. It needs to be in writing. IF BM escalates, you need documentation in order to shut her down.

Additionally, your DH needs to consider putting his daughters into therapy to help them with their emotions around BM. He may also want to try and reach out to BM through a mediator to discuss with her new parenting time arrangements. I don't know what she has on paper, but your DH needs to document every single visit she misses, and if she wants to see the kids, he needs to facilitate it. His daughters need to see her, so long as she isn't a health and safety concern, until they are 18. His job, even though it's a hard one, is to facilitate a relationship between BM and his girls, even if the girls don't like it. 

He also needs to shut down any disrespectful talk about BM. That has nothing to do with BM and everything to do with building character in his girls. What they say privately to one another or their friends cannot be controlled, but in public or around other adults, you two included, he needs to foster a respectful discourse about her. They don't have to like her, but they aren't old enough yet to understand that words have power, and they don't need to have added guilt or anger in them as they age and their opinions change.

If you're scoffing at the idea of therapy and respectful language, I'm going to tell you, as someone who was allowed to speak poorly and freely about my father, I have a lot of regrets about it now and have lost some respect for my own mother for allowing me to "get my way". My dad wasn't a good dad to me, but he certainly wasn't the monster I had painted in my head. As I get further and further into my life, I better understand why my dad did some of the things he did, or better understand why he acts towards me the way he does. I didn't help our relationship, and my mother allowed my anger at him to fester. It has come to a point where I don't think I can repair the damage I've done, and the damage I was allowed to do based on my mom's own feelings towards my dad and her not pushing me to try harder has caused me some resent and re-evaluation of my relationship with her.

Remember, you're raising these girls to be good, functional adults. Being "abandoned" by their mother is a strike against that goal, and while you stepping up helps, it isn't a replacement. The girls need more help and guidance in this arena, and it will be painful for everyone. They may be angry now if they're forced to be respectful or curb their anger or visit BM or talk to a therapist, but in the long run, it's better for them to know that you and DH tried your hardest to do right to raise them AND keep them connected to BM versus them feeling resentful toward the two of you for allowing them to feel and behave that way toward their own mother.