Your MIL reminds me of alot of the nosy, gossiping types from the hall. Isn't it crazy that she can't just come over and be a normal human? I am so glad that I married a girl with non JW parents. It makes the in-law situation so much easier. I wish I had some good advice to offer, but I really don't. Just stick to your guns, and don't let the crazy old witch corrupt your children. Let them grow up not believing in worthless lies. Good luck on future visits.
Dustin