Basically my MIL is on a lot of antidepressants and has a LOT of psychological issues. She's a very nice lady and would never dream of hurting DS but I cringe at the thought of her having him alone.
She is unable to cope with a 5 hour a week job despite having no other responsibilities, she is incredibly self centred (although nice) and her family literally revolve around keeping her happy, she cried her eyes out and got extremely angry because DP placed something somewhere and she was scared she was losing her mind and she just generally loses it over things that are just ridiculous to others.
She's extremely possessive with DP and always says DS is just like DP as a baby and stares at him in a slightly unnerving manner 
DS was screaming with pain from his reflux and she went "I'm so sorry I made him cry" in a really depressive voice despite me saying a lot of times it was his reflux.
She then told me she'd been crying herself to sleep because he had trouble with reflux, which really isn't a rational reaction IMO.
She also makes DP go to the shop to draw money out and he tied her shoe laces once. It just seems so odd for a grown woman.
She takes care of her older grandson a few days a week because it's her daughters son who is happy for her to have him.
I completely realise it isn't her fault she is ill and I always make the effort to take DS to see her every week because I do like talking to her but I just don't like the idea of leaving DS with someone who seems extremely mentally unstable just because her daughter is happy to.
The way she kicks off over nothing worries me as in my opinion if you can't cope mentally with a 5 hour a week job how could you with a screaming baby? (If he was to scream)
I don't think I could relax if she had him even though deep down I know she's harmless
AIBU?