HELP I am (26F) tired of my fiance’s brother's girlfriend treating me and his family like shit. What should I do

The gf (26F), let’s call her C, is one of the rudest people I have ever meet. C and I grew up in completely different lifestyles. C's family is extremely wealthy, they built NFL football stadiums and growing up her family lived on a yacht and traveled, while my family was very poor (sometimes no power or water , and a struggle to get food). L

Because we grew up so differently it’s hard to relate to her when she is talking about anything due to our different outlooks on life and lacks the ability to put herself into other people’s situations or empathize with them. C is an extremely intelligent person , she is an engineer, and honestly smarter than I am, I do social media work and HR. Some of her problems while talking to people are no eye contact, belittles people’s opinions or interests, moves in front of people (mostly women) to block them from conversation, changes subject to stuff she likes to talk about (engineering that goes over my head) , and to top it off She also has a problem of talking through her BF (26M), let’s call him F, when talking to other people. His family has noticed it and she has made me and there mom cry because of how she talks and treats us during a conversation.

To give you a few examples of how crazy she is.

So the first time I ever meet them, my BF (30) took me to there house to just hangout and chill, just the four of us. Play some drinking games to break the ice and get to know them. I guess I said something that was funny and made everyone laugh and when she tried to say a joke no body laugh because we didn’t even know she was trying to say something funny. ( btw this is only 30 min into the planned evening we had just started drinking and it was only 8:30) C then got up without saying anything and left. At first we all thought that she went to the restroom to break the seal but as time went on she never came back out. I told F maybe you should check on her to make sure she wasn’t sick. F went into there bedroom and saw that C got into her pjs and went to bed pouting over the fact we didn’t laugh at her joke without telling anyone. This lead to a huge argument between them while ne and my bf just sat in the living room awkward as hell. We decided to just go to bed as they continued to fight till 12. It got to the point were F just wanted to get some fresh air and go to wawa, he got in his car and left and not even a minute later C is slamming doors running to her car to chase him. What’s crazy is she beat him to the place without even knowing where he was going. His brother ended up staying with us for a week and just cried to us saying how mean she was to him and saying all these bad things about her.

They end up back together and we try hangout again. They invited us to try this new winery (never been to one and was super excited) and it was great. The wine was delicious and we played cornhole and other outdoor games. While the brothers were taking a smoke break it was just me and her. I thought to my self this is our chance to get to know each other. She asked how my trip to Miami was a few weeks ago. My head went racing as I tried to understand what she was talking about because we didn’t go to Miami. I told her that we didn’t go anywhere and have been home. She then asked if we were home when F was staying there and I said yes. Nothing seemed wrong but this was only the beginning. After a few more minutes of talking she said that she has to go meditate and that she does it everyday. The evening is ending at the winery but we planned on going out to some bars that night as well. As we walk out to the cars we notice that C is not with us. F finds her in a field sitting there and tells us to go ahead and they would meet us at there house. Fast forward an hour later, my bf and I are sitting in the car right in front of F's house In the street. We see them driving up and started to get ready to go inside. I started to notice how fast they were going as there car speed towards us. I got my BFs attention to see if it was the alcohol or it was really happening, i started to panic thinking they were going to hit us. He looked up and said oh shit as Last min F sharply turned into his yard and almost drove straight into his house. He jumps out of the car screaming that C needs to pack her shit and get out. Me and my bf just looked at each other while still in our car dumbfounded not understanding what lead up to such a physically aggressive fight. Later on that night, because F stayed with us again for a week, we found out that F lied to C about us going to Miami because she doesn’t like him hanging out alone with us. While they were driving home she began to sscratch and punch his face, grab the wheel, and even tried to jump out of the car on the highway at 75 mph because he lied to her as F tried to keep them alive and not hit anyone else who was driving. My BF took is brother out of the situation before it escalated any further to cool off. When he made a decision to stay with us for a little while we went back an hour later to get his car. We decided on a run pick up as he turns his car on via remote, runs out the moving , gets into his and drives away. Planned work smoothly until his car just stopped. This crazy botch was laying in the backseat with shit covering her to hide from him if he ever came back for his car. The only reason why he noticed her was because she hit her head on the door when the car started moving. That night after the incident F cheated on C even though they never really broke up and by the end of the week they were back together again. We still havnt told her. I also know that F continues to talk to his ex and gets dirty pics from her as well.

Everytime we try to make things work she ends up just being a bitch for no reason. She thinks I’m in a competition with her over social media and goes to extant of seeing that I posted something and has to post moments later something similar to it. She also comments on my pictures saying that I steal her photos which are group pictures of the family.

I don’t know why she acts like this but my BF says it has to deal with her being jealous of me because I’m pretty, nice, and I got proposed to before she did ( she been dating F longer) which honestly would be a stupid reason and really hoping it is not it. This is the first time in my life were I am genuinely happy and not constantly worry about Bill’s and food and she is definitely affecting my relationship as well as my overall happiness. It’s too the point where I want to go off on her and not even have her be at my wedding but I keep being told to be the bigger person but,

I DON’T WANT TO BE THE BIGGER PERSON

I just wanted to have a cool sister in law relationship ,F is debating on proposing, where we could go get lunch together or just hangout . I’m tired of wondering if the stuff I post is going to be judge by her and if she is going to say something on the post about it. I did restrict them for a little while on Instagram hoping that be the end of the social media competition but she found out some how and went on a huge crusade about me being bitch. To the point I wished her happy b day and we made her shirts and she didn’t say thank you to me at all and only thanked my bf.

I am asking for help in my decision to either fully confront her about I it and not tip toe around the situation or brush it under the rug to keep peace and choose a different time to say something, am I just over reacting. My one big flaw is I have anger issues so the first instinct I have is to confront them head on and I know this doesn’t work in every situation but I don’t see any other options.