Maybe she can start a GoFundMe thing until she is back up on her feet? You didn't mention a husband. Does he work? Disability might be helpful. She will NOT be down for "months" either..if it's just gall stones and they take out her GB. I would say 2 to 3 weeks. Thats how long it was for me. Teaching my body to deal without a GB took longer..couple of years, actually....but I could still work. Problem is, I could not accept a job and not tell the employer my...ahem..situation. It wouldn't be right. Then I got breast cancer sometime later, which didn't help. Physically and mentally, I was pretty much a wreck. By age 62, I could get my SS. So for 4 years, I did what I could on ebay, and we lived off hubbys SS and we got roommates.
We asked for nothing (except me attempting to get SSI and denied 3 times) and did our best with what we had. I wish your niece luck, and tell her to not worry about the down time after surgery. Unless they find something else, that is.