I agree with Leed - I would not be avoiding your mutual friends. Go! Have fun! If you run into her extend, the olive branch but I don't see the relationship returning to the closeness you once had. Exes are exes for a reason, that includes friendships.

I believe that people come into our lives for different reasons, whether they stay or not. It seems that you were her crutch for a period of time and maybe she was yours. She's got low self esteem, anxiety, etc. It also sounds like she became angry after you told her the truth... Being possesive and derogatory are not traits of a supporting friend... Although your behavior was not excusable, I can see why you reacted the way you did. Props to you for accepting responsibility for your behavior and apologizing. Not many would do that today.