Hi A.,
My father had his gall bladder out (somewhat emergency - he passed out at work with chest pains, they thought he was having a heart attack and then discovered it was gall bladder so they removed it same day within a few hours of going into the emergency room), it was done laparoscopic (sp?) and he was out within 24 hours since he had no complications. If her surgery was done the same way, I imagine her recovery will be pretty quick as the incisions are smaller. My father didn't need anything more than Tylenol for a couple days, but was off work for a week after because he was doing physical labor (HVAC guy for new home builder, doing stuff on the roof and lots of heavy lifting). He's also not one of those 'tough macho man' types... he is a big baby when he's sick :)
I imagine she'll recover pretty quickly barring any complications of course. I would offer her help for as long as she thinks she needs it... if her husband is as much a jerk as you say, she's probably a pretty strong woman who's used to doing a lot herself anyway :)
Hope you're sister recovers well... she's lucky to have you around to help her out :)