I'm sorry to read this. So, she's been diagnosed with colitis. Have they discussed Crohn's disease with her? Anyway, there are different types of colitis and that would be your next step to understand which one is affecting your mom. Bacteria can cause it. I'm sure they've tested for C dif though. parasites can cause it but am sure they've ruled that out too, right? Does your mom have any other conditions like diabetes or chf (congestive heart failure)? It can be an inflammatory disease, IBS. so, I would work with the doctors to find the root cause of the inflammation and then you will be in a better position to treat it and get it to end. The doctors acknowledge and have found the inflammation but have they worked on cause of it? And unfortunately, it is just a genetic condition.
So, how can it be treated. Medication. They can minimize symptoms and make your mom more comfortable. She can also change her diet and lifestyle to be pro digestive health. Keep a journal in which she notes triggering things that make it worse. Then avoids those. avoid carbonated beverages, eat small but more frequent meals, avoid things like popcorn, skin on fruit and other foods, and nuts. Ask the doctor about the right amount of fiber. Stay hydrated.
Anyway, I'm sorry this is going on and hope it gets better!