UPDATE - I think my SIL’s (23/F) best friend (23/F) is trying to get with my (23/M) brother (20/M) and it’s affecting our Christmas plans

First of all, thank you everyone for all the advice. Unfortunately, my family doesn’t use too many avenues of communication that aren’t in person, so it was hard to communicate to my parents the severity of this situation. <br><br>This is what happened: <br><br>I told my mother about my observation and she told my father. They made the assumption that my brother was the one that was trying to get with her friend. After I tried to convince them that my SIL’s friend had a crush on my brother, they thought I was being delusional. The worst part is that they don’t believe me when I said that she’s flirting with my brother. They think I was jealous that my brother was getting attention. It’s bullshit. <br><br>I tried to explain to them that my brother would never do that. He’s going to propose to SIL when she gets back and that it’s just not like him to do that. I was met with utter skepticism and they thought I was making it up for no reason. When I said that I didn’t want to be around my SIL’s friend, they said that I had to be there for Christmas. They told me that if I didn’t go without telling anyone else in the family about it, they would cut me out of the family. I told them that fine but if anything happens between my brother and her, I’m blaming them. <br><br>My dad basically said “It could never happen” and left it at that. When I asked them what would happen if it did, they still didn’t say anything. <br><br>So the holiday’s going to be very tense.