Hi John, welcome!
It is so nice to see people coming here on behalf of a loved one. It is so important to have family support.
Is your aunt sure she has IBS? What sort of tests has she done? Colonoscopy? I haven't seen anyone with IBS throw up that much. Could she have Crohn's (or and intestinal blockage) or a gallbladder problem? I know you said she's been tested but this just seems fishy that her doc hasn't offered much help.
What sort of operation is the doctor talking about? (I don't know of any operation that would stop someone from vomitting.)
I'm sorry I am not of any help. I really just wanted to welcome you and say how wonderful it is to see you trying to help your aunt.
I hope someone will be along shortly who can help.