She still sees it being her home, where she can come & go whenever she choses and she can do whatever she wants to it. She has her rented house and she has this house....which happens to be the family's home.
I think you cannot afford to wait around in setting ground rules. She doesn't like it b/c everything is your way? Fine, then she can go back to her house and do things her way. This is your house. She's the one who invited herself and started changing sheets, etc. I bet she would have a hissy fit if you went to her house and did anything!
Sometimes, it takes bluntness with a WW. Do not let her come over every Saturday to clean, b/c she's just edging her way into the house. She is nowhere close to wanting to cooperate. She wants back in the house, and wants to take over. So, what do you plan to do about it?
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!