So maybe others with adult step children will chime in.  
definitely put wedding on hold until this is fully resolved.  I'm sorry your DH2B isn't receptive to you needing basic respect.  In your own home of all places ! This SD of yours has some nerve.  She shouldn't be allowed over until she apologizes and can act as a respectful adult and she needs to wait for an invitation. Sounds like you and your fiancé live together already ?? This behavior is ridiculous and needs to be shut down immediately. If you live together you have an equal say in who enters your shared space.  Disrespectful jerks are not on the list ; related or not.  This should be an agreement.  
 

Sounds like simply asking for what you need isn't working.  Is your partner open to counseling ? Sounds like you are okay with the idea of leaving this relationship if need be.  Is your partner aware you will leave him if this is not sorted out ?

First off, I think you should give up trying to have any kind of relationship with the older SD. She clearly doesn't want it and it isn't worth the grief it will cause you if you persist.

Secondly, did he move in with you or did you move into his family home? If the former, then you have every right to  put your foot down about her behaviour in your home. You get to decide who comes over and when, not her. She isn't a child who has visitation with daddy. Make it clear that he doesn't invite her over if you haven't been consulted. If she comes over without an invitation "sorry, this isn't a good time", or he can go and talk to her elsewhere. Call her out every single time she does something that oversteps (can you give us examples of how she behaves like the lady of the house?) - she opens the cupboard doors to see what's in there, "kindly don't do that, it's none of your business", she wanders into your bedroom, "kindly leave my bedroom, you have nothing to do here. Be relentless.  Now, if you moved into his family home, things become more complicated as it would be the only home she ever knew. In that case, maybe plan to buy a new place, for the two of you?

Don't let this uppity troublemaker get the upper hand.

I see three routes in this. First is to just keep doing what you're doing and accept this will be your life. You don't like that route, so let's take it off the table.

Second is to disengage but demand respect. This means you stop trying to have a personal relationship with her, but you call her out when she oversteps boundaries or makes passive aggressive comments towards you. This shows her AND your FH that you see her crap. It also puts the ball in your FH's court to decide how he wants to handle both of you in his life.

Now, when I say disengage and demand respect, you do that with more than words. She changes up plans last minute? "Sorry SD, no can do." Then you go do the other thing you planned. When someone asks why, be honest: "Oh, well SD made last-minute changes without discussing with us first, and I had already made other plans that I couldn't bail on." Shine a really bright light on her crappy behavior in a truthful, matter-of-fact way.

This will upset your FH, but that's sort of the point. He'll be stuck will seeing the truth laid out and be stuck having to choose whether he serves his daughter or acts as a partner with you. The first time you refuse to change plans for her, or refuse to finish a meal with her because of her snarky behavior, or inform him that you won't visit her with him because of her behavior, he will be upset. Often in these situations, the parent is afraid of upsetting their child but don't necessarily want to participate in whatever activity with them. They want their partner there as a buffer or comfort item, which is wholly unfair for the partner. You're an autonomous adult, and you have the freedom to say no even if your partner would like it.

This method could lead your FH to end things with you. My thoughts are good riddance to bad rubbish. Throughout this, you can explain to him why you're doing it: because you're tired of SD changing your plans, you're tired of hearing little digs made at your expense, you're tired of SD overstepping her authority in your home. Just keep repeating. Eventually, he'll change or leave, SD will change or stop coming around because FH backs you up, or you'll leave because nothing changed.

The second route is the only route that provides any sort of hope for a better relationship. The third route is to say eff this noise and leave. I don't know if you're mentally and emotionally in a spot to want to do that, but know that doing so wouldn't be petty or silly. The point of courtship, and even engagement, is to see if you're compatible. Love is the easy part; build a life together is hard. There are lots of great people out there that just aren't great for us individually. Letting a relationship go because it doesn't work for you is the point. If folks aren't willing to do that, then dating is a moot exercise because the goal isn't finding a good, compatible partner but to find a spouse - any spouse.

I'd encourage you to stick around and read both the blogs and forums. There's a lot of great info here that can help you in your decision. Just remember: you can't make enough changes in yourself to make up for unhealthy behaviors in someone else unless you're willing to become toxic yourself. You can't make your FH make changes, so if he won't, you'll have to do what you need to do to maintain your health and well-being.

When sd comes over and acts like alpha female lady of the house in your home, you tell her off is a long condescending "NOOOOOOOO, stop that! This is my home"

if she disrespects you, answers you back, your answer is "NOOOOOOOOO". When i would say this hubby stepped in right away to say "listen to your stepmum" 

in the end your man needs to reiterate firmly to his daughter that she is only that!! His daughter!! Not his wife or romantic intimate partner/fiance and she needs to remember her place.

until that happens, your partner does not respect you because between upsetting you or feral adult sd, he'd rather insult, disrespect and upset the fiance. Thats not good at all!!

Sometimes change can bring out the worst in people. Maybe since he was in a serious relationship before and you were "just the girlfriend" she was ok with it. Now that you are getting married she feels her family is somehow at stake? I don't know... I try to sometimes figure out why someone would act horribly to a parent who has found happiness and love... It is hard to do!

My suggestion would be like some others have stated- Disengage. She doesn't get to call the shots in your house. You can be "professionally respectful" to her, just like any other co-worker you can't stand. Yes.... they still go out on the group email but you don't care what they have to say. You don't let them call the shots or change what you have set in place. 

I think you husband can develop boundaries but right now he isn't seeing her as a "problem". Staying classy and graceful while she raises stinks and cries and yells because she isn't getting her way will help him see. 

And put down boundaries around her visits to your home.  How your SO reacts will be a big clue towards your future together.  If he can accept that you won't play happy family with his disrespectful adult child, then your marriage will be fine.  If he can't accept it I would slow things down for sure.

My SD is a control freak too. Thank goodness she lives 800 miles away.

I very clearly laid out to DH what I needed from him, my partner. This was after a major meltdown I had after being totally excluded, watching them walk hand-in-hand with me behind them, excluded from conversations, not offered food or drink at her house, and more. Until then, I'd been "nice" to my own detriment. I tried too hard, went out of my way too often, spent too much money as an attempt at bonding and being part of her life. Pardon my language, but eff that. She didn't want me to be part of her dad's life, much less hers.

So I disengaged--no more organizing, buying things, initiating communication, etc. I told DH that I expected my husband to be my husband 100% of the time, not leave me in the cold in favor of chasing SD, and there is no room in the marriage for a third person. (He still chases SD, but not on my time.) I support his relationship with SD, but it's entirely up to them. I just won't be invisible or set aside because she demands his attention. Fortunately, DH took a good look at himself and was willing to make changes. It's not perfect, but it's tolerable.

I will say that since I stopped trying so hard to be part of their little "family," that my relationship with SD is better.

I wouldn't go forward with your wedding plans unless and until this man shows you he can set better boundaries with his daughter than he has been doing - it would be folly.  Also the lying to you about it would be a serious red flag to me. 

Don't hitch your wagon to this dumpster fire. Throw this one back. His prior relationships failed because of his evil daughter I'm sure.

I would never again marry a man with 2 adult daughters. You get along with the younger one now....how well does she get along with her sister? How much does she think the drama her sister stirs up is funny? My SDs always competed each other(still do), but banded together to "compete" with me until I removed myself from their imaginary competition.

They are in their mid 40's.  YSD has good qualities when she is by herself, but I would never be in a room with the two of them unless the room was well-insulated with normal people.

You definitely need to address boundaries with your DH before agreeing to marry him. Tell him you aren't a second class citizen in anyone's life or family, you won't be treated like one, and you won't be the sacrificial lamb for him to sacrifice to make his oldest daughter happy. 

He may likely throw in your face that you're just jealous of the unique and special bond he has with his oldest daughter, so be prepared.  He is also is feigning confusion because he knows already how his oldest daughter is and doesn't want to address it.  She will punish him, and he knows it.  

Who is your DH more afraid of losing - his spoiled daughter or you? It shouldn't come down to that, but that's the bottom line.

If you can't work this out before you get married, then part ways, because it gets worse after you get married. 

Maybe I am just tired old and cynical.

Very few disney dads who treat their DD's like their wives change. Its their toxic dynamic that works perfectly for the princess and for daddio well he feels like the macho man. The guy always there for his DD. He gets a rush from this, so does she.

I took the advice of people on this board and cancelled my wedding. I was in a similar situation to you. Things are not great now and I am so glad I didn't go ahead with the wedding. Of course I can't tell you if it gets worse after marriage but it would appear so and I won't take the risk.

You should consider changing your avatar picture. It is possible for someone to use a reverse image and find you on this site - which is the last thing you would want to happen.

Oh no...oh dear!  Please heed this advice.  If you are seeing a red flag, then there IS a red flag.  Trust your intuitions.  I agree with Sacrificial Lamb.  "I would never again marry a man with 2 adult daughters."  I have 2 of them myself, and hell hath no fury like a ...Stepdaughter who doesn't want you in the picture.  Your future SD clearly is one of those people. 

You need to have a "come to Jesus" conversation with you FDH and tell him that either YOU come first in ALL things, or you are moving on.  Trust ME on this one.  After 30 plus years with two adult SD's, I know what I'm talking about and I think I know where things are heading if you don't take control right now. 

Big Hugs and keep us posted!

I hope, hope, hope that you will listen to the advice you have received here, and stop this shit show.

You are supporting an able bodied man who could get a job, but chooses not to, paying for renos on HIS property, and paying for feral daughters outrageous weddy demands. 

You sound like a lovely, caring person, and these ferals have cottoned on to you and are exploiting and taking advantage of your kindness and generosity.

Ferals is a harsh description, but that's what they are. It's the cold hard truth.

Of course his previous relationships before you haven't lasted. No woman would want to put up permanently with this rubbish.

It really really saddens me how many stories like yours that I read on here. Please withdraw from these spongers all financial support, you need to think about your retirement years and supporting yourself. 

Finally, don't beat yourself up because that will just make you sink into apathy again and maintain the status quo. Get angry, but with them! Show them your fighting spirit. 

Walk away from this situation.