I’m very, very sorry that you have so much to deal with. Your letter shows you to be a sensitive young woman who is trying extra hard to be fair in spite of it all.
I wish I had a recipe for making it all better. Unfortunately, I don’t. I would need a whole lot more information to come up with a solution to the fighting. For that reason, I’m recommending that you call up that therapist. You had a successful experience with therapy before. Why not give it another round? Once you’ve made a relationship with a therapist, you have a resource you can return to whenever you need to. She will know your story up to when you left so you don’t have to start completely over. Therapy can help you sort out how best to handle your situation. You could also invite your mom to join you so the two of you could work on your relationship.
While you wait for an appointment, please remember this: Someone can only fight if someone else fights back. You have some responsibility – and some power – in this situation. Just because someone invites you to a fight doesn’t mean you have to participate. You could just say something like, “I’m sorry you feel that way” as gently and respectfully as possible, promise to try to do better (there’s always room for us to do better) and go about your business.
I wish you well.