For background, mil does drive me potty and has done some odd things in the past. She's one of life's pessimists and feels the world is against her although looking in her life's not bad. She's also very anxious re driving and falls out with friends very easily - dh and I struggle to believe all her friends are evil. Last summer she quit her job due to stress (they made changes she didn't like and she doesn't cope well with change.) Gp prescribed pills for depression but she won't take them as she isn't depressed it's everyone else around her who are in the wrong.
Anyway, when we've seen her she's been much happier since quitting but fil is very stressed as they can't afford for her to quit and she's refusing to claim benefits as they'll want her to look for work and she has no intention of doing so. Their relationship is strained and she refuses to talk to him about money.
Last week dh took the dc to visit without me as I was working (we live a fair distance away). Fil wanted spend time with dh (needed to vent) so they went out one morning leaving mil with dc. They expected mil to meet them but there was no sign and she wasn't answering her mobile. They got home to find mil had gone out with dc and her mobile was on the table. No big deal except fil's reaction. Fil confided that mil hadn't left the house on her own for 3 months and he ended up running round the streets looking for her in a panic. Dh was really worried as clearly fil felt dc might not be safe. Turned out they were completely fine and mil had taken them somewhere nearby.
Fil refuses to speak about it and clearly mil didn't do anything wrong and dc were fine but I now feel that if fil thought she may harm my dc I just cannot risk it. Mil loves her gc but if her mental health is questionable I'm not sure that's enough.
More a wwyd rather than aibu.