I don't know anything about the legal side of it, but it seems to me that a lawyer or somebody could tell you what to do. That is like blackmail! I would be so furious to know she would do such an "evil" thing to a child simply b/c she was jealous. How horrilbe!
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!
