I won't go into detail as it would run into pages, but MIL is truely offensive towards me and often to dp. I never ever rise to it because it would not be worth the consequences. She would have a field day, spoiling for a fight and dp believes I shouldn't respond as it makes life easier to say nothing.
Sometimes I feel for my own self respect, I should risk the wrath and tell her to stop. For the sake of dp and dd tho' I hold my tongue. I presume this is the right thing to do.
I must say, if dp and I split up, this woman would be given short shrift by me.