I wouldn't pay much attention to good intentioned (but misguided) relatives who try to tell you that your diagnosis is wrong or your treatment is lacking. You will get much more of this by friends and family as time goes on. A biopsy along with patient symtoms and blood work usually tell the story. Sometimes UC will be diagnosed but years later it is found to be Crohn's (or vice versa) but it's not often the case where UC is diagnosed and it is later to be found to be something benign. If your daughter's protocol is currently working I would stick with it. To make yourself feel better you can run your sister's idea by the GI for his/her input.
dx proctitis in 1987
dx UC in 1991, was stable until 1998
1998 started prednisone, asacol, pentasa, nortriptylene, ativan, 6MP, rowasa enemas and suppositories, hydrocortisone enemas, tried the SCD diet, being a vegetarian, omega 3s, flax, pranic healing, yoga, acupuncture, probiotics
2000 lost all my B-12 stores and became anemic
2001 opted for j-pouch surgery- now living life med-free