I'm so sorry you've had all this going on boople.
As I said last time, her behaviour was dead wrong. I hoped maybe she would come around, but it doesn't sound like that happened.
Finding out that she has got closer to your abuser must be so devastating and I think you are doing incredibly well to be where you are now.
My thought reading this, is that I don't think you even can be the person to 'fix' this.
I think of situations like this a bit like mourning. It sounds like she was complicit in your abuse, and when there was an opportunity to support you, she didn't, and that's the sort of betrayal that can really feel like we have lost someone, and have to engage in the process of letting go. It doesn't mean you have to not hurt, or not want things to be or get better. I hope they do to. But it means that getting support for you, where you can, and processing those feelings takes priority.
Do you have any support doing that? Is there anyone you can talk to?
"In between two tall mountains there's a place they call lonesome.
Don't see why they call it lonesome.
I'm never lonesome when I go there." Connie Converse - Talkin' Like You