Toffee I agree with you, it is a minefield for all the reasons you say. I think it's a shame that you can't just relax and do what comes naturally for fear of being judged as either interfering, over-familiar, nosey or on the flip side, lazy, aloof and uninterested.
Threads like this are a good example. You get one person saying 'My MIL is AWFUL. She comes in, sits on her arse and expects to be waited on hand and foot when she knows I am struggling with a three month old baby. She never helps with anything and even at Christmas we had to ASK her to start laying the table for lunch, she knew we were stressed out in the kitchen but she just sat there reading a book with my three year old, because she liked to play at Grandmother of the Year once every few months and then she fucks off again. She pretends to be interested in him for appearance's sake but she's only taken him out for the day three times in his life and she's never offered to have him overnight so I can have a break, whereas my does this once a month and is an angel. When the youngest was born she couldn't even be bothered to come and see her for the first five days even though she only lives an hour away.'
Meanwhile someone is saying 'My MIL is AWFUL. She's here every flipping week without fail, refuses to accept my boundaries that once a month is enough. She drives me insane, waltzes in and starts unloading my dishwasher and folding my laundry, it's so passive aggressive when I am struggling to find time to get in the shower with the baby feeding on demand, never mind keep on top of the housework. When the youngest was born she manipulated DH into letting her visit while I was still in hospital which made me furious, no thought to what I might want at all, it's all about her.
She comes into my home and takes over, starts making my three year old some sandwiches without asking if it's okay to use the nice ham and pombears. She tries to monopolise DS, constantly asking if she can take him out for the day or have him for the weekend, he's my child not hers. She keeps buying him things to leave at her house for when he's there! How dare she! She's trying to undermine me!'
See? How are these women supposed to know what the fuck to do?