my MIL is kind of weird like this sometimes. Not too long ago, about a month or so ago she got upset with us again because we wouldn't allow our daughter to go there for a few days up to a week.
My daughter is turning 3 next month. My MIL lives 4 hours away and only sees her a few times a year so my daughter isn't too "close" with her. She acts shy sometimes, shes young still and a big suck for her mommy. My mom and my FIL see her constantly and she is VERY comfortable around them.
My MIL has some health issues with her back and as complained lots of times that she can't drive here due to her health, she needs lots of naps, doesn't have alot of energy and so on.
She got so upset because we said we don't think she could handle her for a long period of time, especially how far it is, what if our daughter felt uncomfortable and wanted to go home, 4 hours is far away! As well as my MIL's boyfriend is disabled, not mentally but he can't walk well and MIL has to care for him as she would for a child, give him his meals, get him his food and so on like that.
Well she got so upset because we said we didn't feel ready for her to make the trip like that yet and she got mad and started saying " oh you let paula's mom (MY MOM) take her all the time and it's not a problem. she hung up on hubby again and didn't talk to us for a few weeks.
The worst is she calls FIL up after to talk about us always and he's always in the middle and it's so stressful.