We've spent a disastrous weekend with MIL. She picked and picked at dh (mostly while I wasn't there/ busy) and he got more and more introverted and snappy with the rest of us.
Dh is a fan of a quiet life so didn't confront his mum, instead he tried ignoring her comments but they got to him.
I have suggested to dh that he needs some stock answers - along the lines of "did you mean to be so rude?" :)
But I've been thinking about it and I've realised that the problem is MIL wants everything on her terms all the time. Eg the dc must play the game she wants -not the one they're doing, they must play on the swings so she can push them - not climb the climbing frame, we should take 1 car when we go out - but then she criticises dh's driving etc. 
It has totally got to dh who felt she was criticising him and his dc and his parenting. :(
So, how do you deal with someone who wants everything on their terms? 