So whats up wit her?

That's tough. She may be having second thoughts about her leaving you. Before you ask her out right how she feels or what's up with her. Watch her interaction with the guy. Does she seem as happy as she was when you guys were going out? Does she watch you carefully when you're talking to a girl? Does she seem afraid that you might go out with someone else? She might be doing all of this without the intentions of going out with you again, but making sure that if she can't have you, no one can you know? As her about it if she continues to act this way. Good luck.