Same problems with a particular idiot, however this time not sure if im being over sensitive.
My LO is 5 months old, she's got to that stage of loving to grab your face, lips and loves it when you stick your tongue out. I let her grab my lips but I don't let her shove her hands in my mouth. But MIL sat there for 10 minutes the other day and was letting LO pull her tongue, squeeze it, stick her hands actually inside her mouth and as I say this went on for around 10 mins, which I found a bit weird. Anyway when I got her back her hands were soaked in saliva. I found it gross and quite uncomfortable sitting there watching her do it while partner didn't say anything. I did make a comment that 'yuk your hands are soaked in spit', but my partner shot me down and said oh well it won't harm her.
She's the sort to do anything to piss me off if she has an inkling that it gets to me, so I fully expect her to do this again. But I find it a tad strange, like she's mentally ill.
I think it's a normal thing to do, in the sense that babies do explore with their hands and have no sense that they shouldn't pull tongues etc, nor are they going to be bothered by having wet hands.
It wouldn't make me think that MIL was doing anything deliberately to piss me off, as it's not an unusual thing for babies to do.
I don't know your back story but there must be more to it than this? It's not unusual either for grandparents to let babies do this sort of thing. Is there a reason why you think she is 'mentally ill'?
While of course it is normal for babies to explore like this, I do not think it's normal or in fact acceptable to allow babies to continue with an action that many would clearly be uncomfortable with. I am a big believer in starting to set messages young, and gently removing a hand that goes somewhere it shouldn't and steering it onto something more acceptable is absolutely what I would expect in this situation. With any behaviour I always ask "would a stranger be happy for my child to behave this way towards them or in their house" and if the answer is no then I correct the behaviour. A child finds it very confusing to be suddenly reprimanded for an action which they have been allowed to get away with just because it was within the confines of their own family/home.