Hey there...the procedure to take out gallstones is a very common one, and the surgeon that's doing it is most likely very experienced. The good thing is, instead of opening you up (i.e. an incision in your abdomen) like they used to), if the stones aren't complicated, they'll make a tiny incision and but in a scope that is able to take out the gall bladder. This is better because there is less tissue trauma.
Hi there. Read through other posts here too for additional info for your sister. Gall bladder surgery is not exactly a piece of cake, but it certainly was tolerable. I had laproscopic surgery in the afternoon and went home the next morning. She may feel like her abdomen has been run over by a truck, but pain pills will help with that. She should feel much better within a week, and back to all typical activity within a month.
Good luck and keep us posted on her outcome,