I'm fortunate enough to have a wonderful Mil that i'd do anything for, she's amazing.
the parental situation is / was ..... otherwise. The love of a child for parent(s) is incredibly strong and it takes an enormous amount to drive a kid away - but it can be done. PA comments and behaviour is something that aims to undermine and control you when you're a full grown adult and that is not ok.
I think that yes, this stuff does drive people away in pure self defense. It's what happens when people are nasty, subtly or not. The only way to handle it while keeping some contact is to emotionally step back and to keep calm at all times using the responses in a great book, Toxic Parents.
Keeping calm, not rising to the bait and calmly setting otu the truth of what happened helps. Also, I've found that keeping visits short helps. And setting boundaries; things that they know they can't get away with or you'll leave. Do it once or twice, and they get the message. At that point its up to them to decide if they want to keep behaving that way and driving you away, or not.
I'm afraid that their feelings of resentment, being let down, frustration, anger and spite are feelings that they alone can deal with. Their feelings are not your responsiblity, if you have acted reasonably and fairly as far as you can.
It's a good idea to think over if any GC should have contact or not. Depends on just how poisonous the MIL is