Time. The longer you have nothing to do with her, the more the memory of her will shrink in your mind. Do not try to meet with her one last time "for closure." She has made it clear that she does not value the friendship as much as you have. She is not encouraging you to come around, so you need to move on.

The mind can not think intently about two things at once. When your attention is absorbed by activities that really interest you, thoughts of her will receed into the background. When you find yourself obsessing over her, it's time to find some other interest to put your focus on. Let that become a habit.