I take it that you decided not to ask her to leave after the house loan modification papers were notarized? I don't know how many times you have been back and forth with her with "talks". She seems to know what to do to teach you certain things not to do (you said you had learned your lesson) but you don't seem to know how to teach her certain things not to do. She knows how to get you to suffer the consequences of doing any action she doesn't like. Can you not think of anyway to apply it to her? I wish you could, b/c this talk won't do anymore than the other talks did.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!