Anonymous wrote:
Anonymous wrote:I would forward her message to your brother and say, 'It seems like [SIL] is upset. Please understand that sis & I are staying at the hotel to make life easier for both of you - you are already doing so much by having us over for thanksgiving. Sorry for any misunderstandings. Please let me know how we can help out. Look forward to seeing you

'
This, except I would send it directly to sil. She's probably under the assumption that you guys will show up when dinner is ready (after enjoying time at the hotel pool) and then leave right when dessert is done and not provide any help. (If this is your plan, then you are rude, but not because you are staying in the hotel).
I would also add in the note that you would be happy to come as early as necessary to help with the meal prep and clean up.
Also, if there are a bunch of kids involved, then there's also a good chance her kids have also been looking forward to having their cousins sleep over, which just adds to the disappointment felt by her family.