Trying to bite my tongue... Future Sister in Law

So my fiancé’s family is a bit complicated. Him and his brother’s parents split a long time ago. His dad later met their step mom who came with her two daughters and her son. His bio mom is back in the picture but we don’t see her as often as his dad and all of them. Both his brother and step brother are already married. So they’re all pretty great for the most part and I get along with them pretty well. His step mom told her aunt one night that “I could hang” and I turned to my fiancé (then boyfriend) and said that it means that if he ever left me that his family was keeping me. His step mom loved it and was laughing. He was like “what?”. It was funny.


The problem comes with his brother and sister-in-law. They’re normally cool and I like them as people and like hanging out with them. But.... they have told me lies about bio mom, step siblings, etc while claiming to be helping me so I wouldn’t “accidentally” something and become a target of the family being mad at me cause she did that once and they didn’t hang out with the family for a long time. Maybe it wasn’t lies and it was her experience because of how she can come across (She’s an LPN that talks down to my fiancé when she claims she’s trying to help him with his weight and what he should do. She’s very offensive and it comes out more harmful than helpful.) They’ve also lied about me to my fiancé’s father the night before my fiancé proposed. I cried that night cause I’ve caught them in so many lies. They’ve even talked crap about bio mom, one step sister, and the step brother and his wife. (Ironically, they’ve talked crap about the step brother and his wife my entire relationship with my fiancé and would say crap about the couple wanting to hang out with them. but all of a sudden they want to hang out with the couple more and more like they’re besties). Honestly, it makes me wonder what they say about me to the family.
Since my fiancé started talking to them about wanting to propose they’ve been all about planning and dictating it. I don’t know how they let him buy the ring he did cause it wasn’t as expensive as her ring and wasn’t listed as an engagement ring (which is why he refers to it as costume jewelry).
My fiancé proposed to me right in front of his family (they were all in on it) and she walks right up to me and says it’s all thanks to her and she planned everything and even though he wanted to propose after dinner instead of the next day at the beach like she wanted, that she still planned it all and that him getting my ring was because of them.
My fiancé got it from the beauty and the beast collection cause when we started dating, he was going to rent us the then new beauty and the beast movie one weekend. But I went and just bought it myself a few days early and watched it. It even had one of my favorite actors was in it. I did rewatch it that weekend with him in which he saw the dance scene and said that itd be great for a wedding dance. So it has sentimental value. It was the perfect ring. The actual engagement ring in the collection is big and reminds me of costume jewelry which makes the expensive ring, not worth the price. So yeah I’d rather have the one he got me. It’s perfect.

So since we’ve been engaged for about six months, she has said she will be planning my bachelorette party and everything. She’s not even my maid of honor and I haven’t asked her to be a bridesmaid. She’s just taking it on herself. If I show the family a wedding dress or bridesmaid dress I’ve found, she pulls up more expensive dresses to show me. I have a budget and I am saving up my own money for the wedding that I’m paying for but she doesn’t seem to respect that. She even shows me dresses she knows I don’t like or want for my wedding dress.
But she also says (in front of her husband) that she wished she’d have waited to get married so she could have spent more money on the wedding. He paid for the wedding and let her choose... to either spend more on the wedding or have a bigger honeymoon. She choose to spend his money on the wedding and go over budget on her dress.
They had a good little honeymoon but she’s vocally jealous cause my fiancé wants to take me to Disney and he wants to go to universal cause we both like Harry Potter, and because that’s what he wants and I like the idea, that’s what we’re going to do. She says “you’re gonna have an awesome honeymoon” while visibly being upset about hers not being as much.
Like I said, I like them as people. I really do. But some of the behaviors is annoying. Especially when they lied about me or tried to act like I had a problem with bio mom. They said bio mom came to their wedding dressed inappropriate in short skirt and low top, and was trying to be in every photo like a proud mom (even though she didn’t really raise the boys); after we got engaged I got worried from all their stories about her that I said I could have a dress (or moo moo) in my trunk just in case and she could wear it if she tried to show up inappropriately dressed and that I thought it’d be only fair if we had a family photo with her in it but also step mom cause she raised him and she was there all this time; well they started about how I had a grudge against bio mom (who btw told me that she texted my fiancé while she knew he was at work and that she would whip his butt if he didn’t text back) and they then changed their stories about her behavior at their wedding and acted like I just don’t like bio mom. What the?????
She’s even tried to dictate about my wedding colors and say it should be about season and I’m like I’m gonna do colors of a theme Not a season. But still she goes on.
So, I don’t know how I’m gonna navigate getting through this to get to the wedding. At this point, he’s the best man cause he’s the biological brother but I don’t want to ask her to be in it. I don’t even want to tell her the color of the bridesmaid dresses (when I pick them out) cause she’ll probably be dressed like she’s in the wedding. I am torn between doing a simple dress or getting a fancier one cause of all this. Every step i make is judged and every word they say, I don’t know if it’s true or another lie.
Thanks for letting me vent. Sorry it’s so long. Also I don’t know if I want to do a beauty and the beast color theme or a Harry Potter theme.