Feeling stuck

So all through our high school I had a best friend. She was literally my sister. My step brother who I was really close with lived far away, but decided to come to my house for vacation for 1 month. He met by best friend and literally proposed and married her before he left. She dropped everything to be with him and just moved to Georgia with him (bc that’s where he lived) he’s in the military so he’s always moving. They’ve been married a year now and me and her barely talk bc she doesn’t feel comfortable talking to me about him. Anyways, he came to my house without her for a week and told me he can’t stand her and he’s ready for a divorce and also asked if we could drink one night and get drunk and have a fun time. I told him that’s fine but she called me and told me if she finds out he drinks she’s not going to be happy etc. so she kept texting me while he was at my house asking what he was doing, if he was on snap chat, talking to other girls and I got so stressed out. I didn’t wanna be a fbi Agent on my brother. Well anyways, I told him “look, your wife keeps calling me and texting me asking to tell her things about you and I just don’t want to get in the middle of it” and he told her to stop putting me in the middle of it and now she thinks I betrayed her trust and is so angry with me. I don’t know what to do.. this feels like a middle school relarionship. My brother also told her that I was shoving liquor down his throat and he told me out of respect for his relationship he wasn’t going to drink. But that’s a lie!! He lied to get out of trouble. Can someone tell me what I should do cause I’m lost