If the pain is bad and rarely goes away she must go back to her GP. I have suffered with "ibs" for over 40 years and tried every test and diet under the sun. I knew I had intolerances to things in my environment and while I was not allergic in the true sense, I knew some foods and medicines were problematic. When things have become bad I have cut out salicylates which helped, other times gluten, and dairy. Sugar is the worst for irritating the bowel, that should be the first to go. It's not good to cut out whole food groups for long unless there is a proven allergy to them. I use the FODMAP diet now and I think it helps but who knows? In recent years I was diagnosed with EDS hypermobility so my "ibs" would be associated with that. A doctor has spoken to me about Mast Cell Activation disorder and it shows the same symptoms as IBS. There is no test for it yet but it is known, It's like an allergy and controlling the diet is the best way to deal with it. Another tip is eating only fresh foods, nothing reheated, nothing that has been cooked and around a few hours, no processed foods, sugars and following the advice on the FODMAP diet.