It seems to me that the best solution would be to forget about this girl and move on. The problem is that she hasn’t let go of her past, and this will not allow you to build a normal relationship.
I've had that experience and I know how painful it is. I liked the guy and he liked me too. And then it turned out that he couldn’t forget his ex. He was writing to her, sometimes calling, especially when he was drunk.
And then he apologized to me, saying it was all a mistake. I apologized a few times, but when it started happening regularly, I got tired of it.
The only thing I regret is that I did not end this relationship before, but lost so much time and nerves.