Your opening statement said it all.
You dont want to have a relationship with her - thus you are sending out the negative vibes already.
I phoned my son to ask for money - not to have the money - I wanted to see him. I had hoped he would show his face and visit. Sometimes parents will reach out in a rather strange way...
Dont judge the book by its cover. Get to know your mother in law - she might be a normal human being with longing for her child.
Why not reach out and share the beauty of the person what is reflected somewhere in your husband?