Cut her loose! And even if she contacts you after a while saying she misses you, it doesn't mean she really cares about you.
It just means she wants your attention and she likes playing around with you and your feelings. Unfortunately there ARE evil bi&@#&s in this world that enjoy screwing with our heads.
Only give her a chance if she actually PROVES that she changed and somehow miraculously realized you two are supposed to be together and acts on that. But that's a highly unlikely scenario...
I'm sorry for being so blunt bro, but I've dealt with this type of girl before. Going on insisting and hoping she'll be with you only brings you more pain. Letting her go will be hard, but well worth it, trust me. Try to forget about her and focus on something else.
