I agree with borderline personality disorder being a strong candidate. Even if she doesn't have the full disorder, from what you describe she has certain symptoms. Given that a personality disorder was suspected as a child, this makes BPD even more probable.

Without treatment she may not improve at all. Sometimes BPD does lessen with age, but don't count on that as being a cure all.

If she refuses treatment (which many borderlines do.....hence why they're stigmatized extensively in the therapeutic world), then you'll have to decide if you can live the rest of your life with her being exactly as she is right now. (Please don't think love is enough----it's never enough to overcome a partner who refuses to help themselves.)