I got so confused reading your question. But I think I know what to say. There was this girl I met at the psychiatric day hospital I went to for two weeks a few years back. She has a fucked up history of trauma I'll say that, but we became great friends. I thought she was awesome and she soon enough felt like a best friend to me. I let her into my home and we hung out a lot, sharing trauma, being whatever. But this girl liked my older brother. I didn't mind, thought it was interesting since I think my brother is a jerk to me. But I allowed them to exchange numbers. They started dating a few weeks after chatting and became a couple so I saw her more often. But then, she and one of his friends started hanging out a little more. She one night told me she's going to break up with my brother, blah, blah. I felt sorry for him, they broke up, all is good I guess. Until she told me she started dating his friend. I was shocked because she even asked me to keep it secret from my brother until they confess to him as a couple. And fuck, I just shut up because I hoped I could preserve our friendship. Man was I stupid for choosing a cheating girl over my own brother's feelings. I also got in deep shit for hiding the truth, even though I was too scared to tell everyone. And now, I'm not friends with her anymore. I don't trust people anymore.