why would my drunk ex Starr crying after seeing me?

This girl ended things with me 2 months ago to get with a mutual friends of ours, I was extremely kind to her and treated her right during our 2 month stint. She wanted to stay friends but I told her no and removed her from all social media and did the same to the guy I told them both face to face we are no longer cool at all. They are also both in my class so we see each other everyday. she pursued me BTW in the beginning and he was pursuing her at the time but she went for me. But this past Saturday we were all at a party and as I walked she was at the door and drunk and when I walked by her she said to another guy that she hates me.. I don't know why she would hate me, I just stopped speaking to her and act she doesn't exist, I didmy spread any rumors Either, 30 minutes later she's on the couch crying and as I walk by her, her friend asks her why she's crying and she points at me and said because of that guy. I just kept walking like I didn't hear or see anything, and the guy she left me for was also there, I haven't spoken to either of em in 2 months, but why would she even hate me? and why would she cry? I'm the one that got walked all Over..