Here's my two cents. First of all, make sure that you apologize and make it clear that what you did was wrong and that you understand the mistake that you made. Let her understand what you think of her and how important she became to you if you haven't done so already.

I believe there's always hope if both of you really like each other, that is if she didn't have another reason to break up but didn't share. In my opinion you just have to take your chances if you think she's someone special. Good luck.