What's wrong with her. It's nuts. And yes hard to let go.
I hear you. And maybe you have isolated the non's three jobs?
Job 1: What's wrong?
You've decided she likely has BPD. And if this is true, you need to really accept this, and what this means. Which leads to Job 2... .
Job 2: It's nuts.
It's good to know how the nuts usually happens. If you haven't already, maybe look at the DSM-5 criteria and read other summaries on this site, from the Lessons. And then maybe it will be easier to understand and accept that the BPD person will do things that are unpredictable, irrational, and which you don't understand. And they will do them mostly to the person who once was their closest ally. So you can plan that these things will happen again while you are in contact (since you have a divorce coming). And they're not personal. It's the disorder. Even in cases where it's obviously done to get back at you, to hurt you, it's still the disorder. And they didn't choose to have the disorder. It happened to them. They had no choice about it.
Job 3: "Hard to let go".
Yes, because we are programmed to be emotionally linked to people, to bond to them. But not impossible. The link gets weaker the less we trigger it. So we need to work out ways of cooling out, avoiding the enmeshment. It will be hard for you for a while because of the divorce. But still you need to minimize it.
There's a great post on this site, I've forgotten the poster. They say that when they get into a rough state relative to their BPD person (who they are staying with), they repeat 5 times to themselves: "I chose to stay with a person who has a serious mental disorder... . "
Maybe something like this would be useful, as a way of letting your own emotions calm a bit... . ?
And/or going to a therapist, if you're not already?
Sometimes the final piece in the puzzle is starting to look at our own stuff. It was for me. I spent waaaay too many years carrying around a puzzle with one piece missing.
PP