I had my meningioma 8 hr surgery back in October. I was in the hospital 2 days and very ready to leave by the third day. I also was on the pain meds only one day after that - then some Tylenol once in a while. It was not too bad!
We really appreciated a few family members around. REALLY appreciated a few meals folks dropped by. That's maybe the best way to help and show your support. Everyone in the home with the patient will be recovering from the ordeal too and no one wants to plan and fix meals. At least that's how it was for us.
Daily checkins even by phone or text for the first week or so were appreciated. Maybe one family member could send updates to a list of those wanting to show support so only one email or text informs many. That worked for us.
Hopefully your sister-in-law will be able to enjoy relaxing with frequent naps and movies, etc within the first few days! It's great that you are supporting her!