I agree that you should not discuss your W with her mother. Your W would be livid b/c that is her mother and she wouldn't feel that you had "rights" to discuss the M with her. In fact, she would probably be okay with anyone else except her parents, first, and other members of her immediate family, second.

It also puts the MIL in a bad position, even if she wants the M to work out. She has to keep a R with her D open, even if she doesn't agree with every thing her D does.

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!