Hi, so my FI's younger brother is freshly 18 (lets call him johnny) and is going to be the best man. He is in a relationship (lets call her betty) for maybe a year now and at first she was nice and i liked her. Fast forward to present, she has done some really questionable and rude things that make me side eye her all the time. She has basically openly said she does not like johnny's family and barely comes over and if she does she makes it a point to keep johnny away from all of the family. She is quite rude to all of us especially to my FI and my FMIL, yet my FMIL is very nice to her for the sake of johnny and keeping peace. I know etiquette says that everyone in the wedding party should have a +1 even more so if they have a SO. However, since she is so openly rude and we all know she doesn't like us, do i still have to invite her? I really do not want to but for johnny i feel like i have to. My FI doesn't want her there either. We are both worried that she will take johnny away from the party and family like she did at out engagement party (they went off twice and the first time we found them and asked them to please stay with the party and she said okay we will and 15 min later she was gone along with johnny. When FI found them he got mad at johnny and said "i asked you to stay, why did you leave?" Johnny then said betty said she didn't want to be here and she is uncomfortable around everyone so she made me leave). I know they are still practically kids but I don't know what to do! Any advice? thank you!