Im married with a 4 and a 6 year old. I have a sister who is 24. She graduated from college and got a decent first job but got laid off about a year ago and has been living with my parents since. I think she may have had some service industry jobs here and there but generally hasnt worked much in the last year. My wife and I have good jobs but try to be relatively frugal because kids are expensive.

My wife and I are planning a trip to Disney with my SIL (wife's sister) and her husband, and their 5 year old. My wife and her sister are very close and her husband and I are decently good friends these days.

My sister heard about this trip and is really clammoring to go with us. We never went to Disney growing up and she said she's wanted to go forever and really wants to go with us and the kids. She however would not be able to pay her way for the flight/ticket/ and all that. We'd expect to sponsor her it would all in all cost us about 1k. My wife and I talked about it and decided it would be worth it to us if she would help babysit some of the nights so we could have some just adult time. So we offered her this, thinking it was generous but a win win for all of us.

Long story short she felt otherwise and said were trying to take advantage of her and treat her as a nanny not family. I think this is kinda ridiculous as she's not my kid so in my mind there's not reason to pay for her just because if she's not doing anything to be helpful. Would like some feedback from neutral parties if Im asking too much.