"Because! I broke up with you and started seeing someone after you beat them up and my sister beat you up and I'm the reason you're here and if you hadn't come to the ball you wouldn't have gotten stuck here." Why wouldn't he hate her? Megan certainly hated herself for what she had done to Stan.
"I mean, I understand why you hate me, but I didn't mean for any of that to happen and I don't mind if you blame me for everything, but it's kind of hard to be really nice to someone when you know they can't stand you."