Lardybump, will be watching this thread, as I could have written more or less the same thing.
Mil snatches the girls as soon as they are in sight, and will hold them forcefully even when they try to escape (you know that thing kids do with their shoulders, you just can't get hold of them, i call it "slippery snake").
She has now resorted to lying about it all saying "ooh Regina is out aaaalll the time, so i have to have her DDs overnight".
Not true.
She once dropped DD1 when she was 7 months old, and never apologised, just said it was the baby's fault. . We ended up taking her to A&E as she was sick (DD not Mil), Mil never even called to see how she was.
From that day, I said "that woman isn't going near my DDs".
Dh understands (although he would like the situation to be different).
DD1 and 2 love her to bits, but they just don't question why I am around all the time when Mil is. They can enjoy her company this way.
(i have a long list of unbelievable things she suggested to "help" me care for the babies, but that would be a whole different thread, i have already hijacked yours!! Sorry!)
All this to say, you're not alone.