My boyfriend's mom (55F) is saying I am manipulating him (22M) into hating his family

Tldr: I defended myself against my boyfriends twin sisters condescending comments and now his mom is coming after me. I have decided to not come with them to Christmas over it and now I am being outcasted.

I posted this in another sub but was told that I might have more luck in an advice sub. This is my attempt to hear some opinions. Hopefully it doesn't get swallowed into the void.

My boyfriend (22M) and I (23F) have been dating since last August (16 months) and have been very happy. We have good communication, trust, and security, and most importantly we laugh together so much. Everything has been great, but with great things comes compromise.

My boyfriend, Vincent, grew up with a twin sister, Megan. He has always been the more outgoing and infectious one, while his sister has sat on the sidelines and has been the calmer of the two. I think a lot of the problems in their relationship stem from jealousy on Megan's part. Vincent was on a path to becoming a national athlete, has excelled in everything that he does, is working on a master's currently, etc. Megan hasn’t accomplished nearly as much and I can see where she might be resentful.

Since the age of 10, Megan has bullied Vincent. One instance that he has shared with me that has never left the depths of my brain is that one time during high school, he thought that he had ruptured an organ. He was in a lot of pain, couldn’t lift his arms above his head, and was physically struggling. He asked his sister if she could please help him by carrying his backpack. She told him no and didn't help him on their walk home.

This is one of many times over the years when his sister has mistreated him. Their mom, Deb (55F) has never really punished Megan. Instead, when Vincent defends himself, he gets in trouble and is told this is just how his sister is and that she apologized so everyone should just move on. They are 22 years old now, and Deb still gets involved in their affairs and navigates it like this. Vincent had been in low contact with Megan until they were about 19. She had claimed that she wanted to have a relationship with her brother and was trying to change. It has been going exactly how you think.

I have seen Vincent's sister blow up at him multiple times since we’ve been dating. I usually try and stay out of it because I do not want to make it any worse than it already is. However, this all came to a head last week. We had gone over to Megan's house for a small get-together. We were the first ones to arrive and we had brought some of our own snacks and good energy. She asked us if we wanted to play music and we said sure. I pulled out a bag of chips and she made a snarky remark about whether or not they were from her pantry. Okay, just a misunderstanding.

Vincent and I were dancing and having fun. Her friends started arriving and the dynamic shifted. I had already felt unwelcomed but when her friends arrived, it became painstakingly obvious. Everyone eventually went to the garage to smoke. Vincent and I were not invited, but Vincent is a social butterfly and went to the garage anyway. I came with him because we were there to have fun so let's try to have some fun!

They were passing around a joint and offered us some. Vincent said, “Oh I’m down I just don’t want the roach.” Well, we were in luck because they had just packed a bong! He takes a drag and the downstem comes out along with the bowl and falls. The downstem chips and it doesn’t seem like a big deal but oh no, let me tell you. Megan gets in Vinceints face and is yelling at him, calling him “fucking stupid” and repeatedly saying “Well are you going to buy me a new one? Where are you going to get it.” Overall, being so ugly. I am sitting in the further side of the room, steaming. I try to diffuse the situation by saying, “Hey, it’s no big deal they sell these at smoke shops. You can easily find another one.” She turns to me and without missing a beat says something along the lines of “they don’t always have the right size” or something to that effect but in the most snarky, condescending voice you can ever imagine. I get upset and I tell her, “Megan, don’t fucking talk to me like that.”

She immediately comes after me, what a shock. Instead of arguing about what is happing in the present though, she starts throwing shit in my face that happened during Thanksgiving, saying I’m negative and I had my nose in a computer the whole day when we were supposed to be around family. To preface, I was writing my college thesis. I had a lot of deliverables due that Saturday and I was panicking. I was anxious, yes. But it felt really low of her to go there with me.

At this point, I am trying to not lay my hands on her. My adrenaline is skyrocketing and I am trying to calm myself down. The room eventually goes silent. My boyfriend tried to break the tension by making jokes about the situation. They were funny, but I couldn’t bring myself to laugh. Megan again, makes some snarky remark at me to try and get a reaction. At this point, I just left.

Vincent came outside to talk to me and calmed me down after about 15 minutes. He went back inside to collect our stuff and Megan tried to follow him outside. He told her now was not a good time and we left. We ended up going home and watching a movie and had a good rest of our night.

I was supposed to go to Christmas with him and his family, but after this, I decided it was better if I stayed home with my own family. I felt that it would be uncomfortable for me to go and it would not be a good atmosphere for me. Plus, it would require me to take off time from work which I can’t afford to do anyway, and find pet sitters. So honestly, it worked out better for me to not come anyway.

The next morning, his mom called and they discussed what had happened the night before. Well, I was mistaken when I thought she would see our side of things and be sympathetic. No. She takes Megan's side while saying “I am not defending what she did but you need to forgive her and move on.” Sounds like you’re defending her in my opinion. I also want to note, I still haven’t received any type of apology or outreach from Megan.

Vincent then gives me the phone, I am not interested in talking but I humor it because I have involved myself in such a way that rocked the boat. His mom immediately starts attacking me, telling me that I need to “step in line or you will be outcasted and sidelined.” What the fuck? I defended myself against mistreatment OVER A DONWSTEM and I am being told that if I didn’t just lay down and take it, I am no longer welcome. His mom continues saying how hard she’s tried to accept me and that she just wants her son to be happy. She then goes on to do exactly what Megan did and throw Thanksgiving in my face along with other things including me demonstrating vulnerability with them and talking to them about current events in my life that had caused me distress. Well, no more.

Deb is trying to bully me into coming to Christmas, saying if I do not come it will cause a rift that will be very hard to overcome. All of the blame for the situation is being placed on me. I am being used as a scapegoat as to why Vincent doesn’t have a strong relationship with his sister. As if this has not been going on for years. Deb texted Vincent, saying I am manipulating him into hating his family and that I am very hard to like. She insinuated that all of his friends just deal with me for the sake of Vincent.

I am really hurt by all of this. I am unsure how to navigate this any further. I am worried about it damaging my relationship with Vincent. I want to move past this but it feels like I have an elephant sitting on my chest. How should I move forward and is the relationship with his mom and sister worth saving?