I'll raise a point that nobody has. At what point will this eventually begin to make you ill? It's really admirable that you are standing by this girl, but you are opening yourself up to an emotional nightmare. This could well be behaviour that will repeat itself over and over again. Do you want that from a life partner? I hope I don't sound harsh, but I can relate to your girlfriend/ex girlfriend. I've been there and done it myself, more than once I've behaved how she is, and I've ended up making partners ill with my behaviour. I'll to the point that they have had to take medication themselves. Somebody mentioned the word toxic earlier. Sadly, that can and has been me in a relationship.
Do your best by this girl, if you chose to take that path. But please, don't let this girl make you ill. There's plenty more fish in the sea.