It really isn’t so sad — as much as it is unfortunate. What I mean by that is that your brothers have exactly the right approach. If you don’t set the boundaries — your mother can’t and won’t. By allowing her to stay too long — and talk too much, you were giving her permission to stay exactly the way she is.
It is better to feel a little bit guilty and not so resentful. The resentment you feel towards her is so great that you’re waiting for one of you to die. Learn to say no to your mother. Just because she wants to do things her way doesn’t mean that way is okay. Instead of picking up the phone and talking to her so many times a day cut back. You’re not going to heal your mothers abandonment issues. She needs to do that with a therapist-not by demanding you lose yourself to make her happy. You are abandoning yourself in the effort to not abandon your mother.
It is new behavior for you, but I’d rather see you feel guilty for saying no — than wishing one of you were dead. You may want to have some individual therapy along the way to get support for doing this. The find help tab at the top of the page can help you find someone in your area.