My opinion only...

You do what you think best for you, let MIL deal with HER issues with her daughter...

Stay away from that one is what I have done and would do again, though MIL hasn't really put me in the position the way yours has:

"She told me w would respect me more if I put a stop to all this."

BS on her, that is rather manipulative, imo.

What does your "true" (ie, quiet) gut say?

In the depths of winter, I finally learned that within me there lay an invincible summer. - Albert Camus

Uncertainty is the very condition which impels people to unfold their powers.-Eric Fromm