First of all, I want to thank all of you for your responses! As I read each one I thought, " And THAT'S why I asked the BBB!" You've all given me a lot to think about, especially Gatorsmom, Green-Tea and niccig and followup comments that came from those posts. (not meaning to leave anyone out here- honestly each response is so helpful. Those just kind of struck me for some reason.)
A few things. We have rented a house for spring break (in state) about 2hrs away just for a change of scenery, so neutral ground. DH will definitely be talking to MIL before we go. It could go either way with her - Oh ok i get it or FINE I'm not coming. And of course we'll be talking to DDs, and hopefully coming up with guidelines/plans for dealing with foolishness.
I have been in these scenarios before with her. EX: her packing her bags and calling the airlines to change tix (when she lived far far away), because I called her out on using a disrespectful term about a gay couple. And I was very casual like - oh you probably shouldn't use that word - it was a DRAMA. (Heck I probably posted about it. ) I told DH the second she pulls the "I'm going home" card I'm throwing her in the car and not stopping til she's on her doorstep.
Also wanted to add she's not abusive to DDs, but they just get disgusted with her viewpoints. I swear sometimes she starts it by picking up on something DDs say in passing, or just dropping a comment to see how it goes over. I can't decide if she's really doing it on purpose. Just for perspective MIL loves playing both sides. "I can't believe they speak to me that way in my own home!" and also "I can't believe someone speaks to me that way as a guest in your home!" So yes she always can say what she wants and we can't.
MIL is a challenge.