I echo Zanne and can't add much to her input. There is no question that her diet may need to be modified to NOT
exacerbate the condition. But as to the diets you mentioned, it will be strictly a trial and error basis for you guys.
If the diet is a concern, a food diary may be a help to you to compile a list of things for her NOT to eat. And watch for certain ingredients, like MSG, onions, polysorbitol (and the like for me) or whole grains, huge amounts of fiber. It is hard to say exactly because the disease is Sooooo individualized which is what makes it so hard to treat. Literally no 2 of us are alike in our symptoms, how the meds work and what causes pain/flares/problems.