Gall stones can be managed with diet so unless your friend is extremely sick I doubt the drs will do the surgery until after delivery because it can be risky.
I had gall stones and pancreantitus while pregnant and I didn't have my gall bladder removed until 4 weeks after I delivered my LO.
Some surgeries can be fine. Will they go in through her back or sides? I can't imagine they'll be able to go through her front because of the uterus. I know some women have appendectomies (appendix is removed) while pregnant.