Just back off for a while. She's obviously not ready for another relationship, and you were pretty much just her rebound at the time. It doesn't mean that you guys can't be friends, but don't expect her to come back around and want to be in a serious relationship with you. On the other hand, she may get over him and come back to you. Just chill and keep your options open.

In other words, don't put pressure or unfair expectations on her, just let her get over things and make up her own mind.