I think the best thing you can do is cut her loose and give her a clean break, for two reasons. Firstly, feeling that abrupt loss on her end might trigger the emotional response needed for her to recognize that she made a mistake (dumping you).
If that doesn't pan out, you can at least have a fresh start without that heartbreaking feeling of wanting her back but never quite being able to have her because you're "just friends."
Give her the gift of missing you, let her existing (girl)friends be her friends, then see where that takes you. Tough situation though, my sympathies.
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