How Can Vomiting And Diarrhea Be Treated?

My friend is 67 and has been vomiting and having diarrhea for 3.5 months now. For the first 2 months daily. Now it s about 1-2 days a week. Colonoscopy came out normal. She will often wake up feeling fine, but come midday she is nauseous, then begins throwing up, which then starts the diarrhea. (However, the first 2 months it was diarrhea first, then the vomiting would follow). She also has a dull ache on her right side. It gets worse with the diarrhea and vomiting. Appendicitis, kidney stones, diverticulitis, and diverticulosis have been ruled out. Also, the doctor seems to think it s completely unrelated, but three weeks ago she all of a sudden had an abscess grow on the right side of her stomach in the skin. It was at least the size of a 50 cent piece in both width and depth. And was visible by just looking at her skin. It was almost on top of where her side aches consistently. She has never had anything like it before.