If she works, and he goes to the Nursery - she’s probably feeling guilty for not being a full time Mum. hence possibly over compensating by taking him out to have fun when she is there - any young child is hard work - even taking them out for ‘fun’ can be exhausting. Father doesn’t seem to be in the picture much from what you are saying, and her asking why you don’t enquire after them, could be a subtle way of saying she is having some troubles mainly coping on her own?? Right or wrong, she IS keeping in touch regularly with you, and many don’t even have that . The fact that her Grandfather is 90 doesn’t mean she has to keep in touch just because he’s elderly - my Ex is 87, and his own sons don’t like him much, but try to keep in touch, and send pics of the grandchildren etc (the one son lives in Japan) despite the fact that EVERYTHING they do is ‘wrong’…he is the most self-centred bully I’ve ever met. His current wife does all the work for him making phone calls, and making all the appointments etc, etc, nothing to do with him being unable to - he isn’t just won’t. She sends texts, etc, he will only occasionally speak on the phone.
He complains they don’t ask after him and his health constantly, but rarely asks after theirs.
I agree with those who say just get on with your own life, reply briefly to pics, etc, when they come through and do ask how your daughter is - she might be struggling??? The ‘life is one long party’ may well NOT be accurate