M.C.
I'd have a little attitude with her too if she was looking after my brother that way too!
Actually, I suspect your daughter is the one really watching him for the most part and thus the attitude as well. I suspect she is just being protective and resents "the someone else" (mil) not helping her.
She would never ever keep either of my children again.
(especially since she has a pool)
She has twice (that you know of) shown very poor judgement, both of which could have resulted in something tragic.
Kudos to your little girl, give her a big hug and kiss for me. She is more responsible than your MIL.
good luck and God Bless!