If possible - can your new DH take care of the SD, teach her the basics himself? My Dh has just recently taught SD13 how to clean a bathroom all by herself, for the first time (gasp!) It gives kids a sense of accomplishment that they can take care of themelves.

I feel sorry for the kiddo - this is all new and different for her. She hasnt been raised the same as her siblings obviously and she sounds very delayed. And if her mother has mental issues, then chances are good that your SD has them as well. This happened with SD 20 Feral Forger - her personality is JUST like her mothers.

My favorite answer to lying thieving Skids - nanny cams.

You have a few options...but I would really recommend marriage counseling. A second option is to disengage from SD. But this should be done for you and your sanity... not to punish others.  The final option is divorce
It sounds like you have done all you can do... now you need DH to meet you half way. overall you say you are happy... but the issues with SD seem to be the root of the problems. You mentioned several issues such as lying, poor hygiene, not picking up after herself and a general lack of self suffiany... what does DH have to say about these issues? Why are you fighting over them? Is he bothered by these issues?

it is your life and you must make the decisions that are best for you!! But... if I were in your shoes and was otherwise happy and in love with my DH... I would try and understand his point of view... and make sure he understands yours. That you are not complaining because you simply don't like her... but that the hygiene and sanitation effect others in the house, they lying should be meet with consequences not matter who she lies about, and the not knowing how to be self suffiant will make her life more difficult. These are things that need to be addressed so that she develops into a happy healthy productive adult.

keep us posted. ❤️
 

DH fought so hard for his daughter, now HE needs to be the one to parent her, not you. 

I was faced with your exact sd situation when I got married earlier this year. Dh thought I would do all the parenting just like his mother was doing for him before we got married but nope! Not happening! I wrote out a schedule for homeless looking feral child sd9 and told dh when it was time for her to move to the next item since dh was unable to parent on his own. 

For instance, 6pm is dinner. 6:30 homework. 7pm shower. 7:45 snack. 8pm relax in room. 8:30 bedtime. Dh got the hang of it and when she resists moving to the next item on the schedule he just shrugs and says “well that’s the house rule.”

Have boundaries and stick to them! Sd9 is mentally challenged at best so each life skill that is taught to her takes several months to sink in. We still haven’t conquered flushing the toilet, but we’ve only been working at that for 3 months. We work on improving 1 disgusting habit at a time with her. 

Dont divorce your hubby over the kid! She’s not worth it! 

simple, he teaches his daughter basic hygiene, basic respect and to be civil but your husband refuses to

Why did your husband fight for her so hard if he didn't really want to parent? Parenting is not all about the fun stuff and spoiling them. I think you need to have a serious talk with your husband about stepping up and marriage counseling. Let him know that those things are a deal breaker, and if they don't change, you won't be able to stay in the marriage. Then follow through. And it will be hard, but stop caring more than he does. Disengage from your SD. If she makes a mess, point it out to your husband. If she doesn't flush, tell DH to come do it. When she asks a stupid question, tell her to ask her dad. Don't cook for her, don't do her laundry, don't pay attention when she doesn't shower and reeks to high heaven. He'll get tired of doing all the stupid little things she should be doing, answering her dumb questions and smelling her rank ass. 

Give him your bottom line and mean it. No one should have to live like that, and you have your own worries with your kids, ain't no one got time for a feral child that isn't theirs. If your dh can't step up, either leave him or insist her give custody back to BM, because he clearly isn't willing to parent, and it shouldn't be left to you or not at all. Let BM deal with the little animal she helped create, this is not your responsibility. 

Maybe have a come to jesus chat with your husband that he HAS to parent his child in your house. He does not have the option of throwing a tantrum (really?) or walking away. You are alowed to walk away because she is not your child and you have plenty of other responsibilities. I might also suggest he take a parenting class, read a book or get some help to keep his temper in check (does he have mental health issues that need adressing?) and some advice as to how to encourage good habits, he might take it better from a professional than you (and it shouldn't be your job to teach him). 

As for you, learn all you can about disengaging. Here are some ideas of things that might help:

If she asks you anything say ..."ask your dad" ..if he isn't home, she can wait until he is. 

Let her hair be a mess. It is not your problem. If she complains to you about tangles tell her to ask her dad to help her. 

Don't worry about teaching her life skills such as cooking - dad or mom can teach her or she can learn from youtube when she is older.

If her stuff is in your way, 1. tell your husband to move it, if he isn't there (or refuses to do it) have a box that you can throw it in and her dad or your sd can find it there. When the box is full, instruct your husband that it has x days to be emptied or it is all going in the trash (and then follow through with it). If it isn't in your way (ie it is in her room) close the door and ignore it. 

If you can, have one bathroom that sd is not allowed to use and you only use that bathroom. Your husband can deal with the flushing issue.

Encourage your husband and sd to do activites out of the house together when she visits. Maybe some afterschool activities and sports on weeknights or time at the local library so she can do her homework there and day trips or hikes out with dad on the weekends....basically anything to get them out of your hair. Equally if you can get out with your kids then go for it and leave sd and your husband at home. Perhaps a couple of strategicly planned visits to your relatives for the weeks sd is with you could help your husband pull his finger out and step up on the parenting front (and at least give you a break). 

If you can aford it I would consider getting sd a laptop/pad or something else for her to use at your house. I know it is an extravagance, but honestly if you don't want to have to deal with her it will keep her out of your hair. (My 11 year old step daughter spent most of the summer with us on her pad playing games on roblox). DO NOT let the pad/laptop disapear to her mother's house - it may never return. 

I've heard that the book stepmonster by Wednesday Martin is good for learning about disengaging, if you've time I would give it a read.

No he checks out and hides in the room or throws a tantrum and doesn't want to deal with her. Which leaves me to pick up the slack.

Your H doesn't get the luxury of "checking out". He fought for his daughter and now he has to parent her in all ways. I"m willing to bet that he was relying on you to do ALL the parenting and when it comes to disciplining he doesn't want to come across as the "bad guy". This is all part of being a father and sticking his head in the sand and hiding will not improve anything. If he wants to save your marriage he really needs to step it up and change.