It's hard to let go of an old friendship. Especially a toxic old friendship!
If anybody is weak here, it's her. Just saying.
She likes having you around to kick about. Makes her feel good (see 'weak', above). It's why she wants you back on the scene, her little bit of sport.
I've had to have a bit of therapy to discard old toxic friendships (frenemies), probably bcs I chose them when I was up to my neck in toxic family stuff and didn't know any better. Then you get into that terrible loop, like with your parents, of hoping they're going to change, especially as you've put so much effort and time into the relationship.
She isn't going to change, not in a million years. The only thing you did wrong was choose her in the first place (what you were used to). Cut her loose and fly away, free of this dead weight pulling you down to the pit.
DON'T see her again, hoping she's changed. She'll never change, she is toxic, and you'll only get dragged down all over again. As you have been this time xx