Long ago I had a friend who had 2 children with Celiac Disease. Both boys took Digestive enzymes with every meal to help them digest their food. I don't know if they took Pancrease.
I guess this would be a lifetime even for these boys, but they moved away and I am not in touch anymore. I know they were bright, active children even though they had to have chest percussion and other respiratory treatments every day too.
I am sorry your sister has so many troubles to work with and wish her well with her upcoming surgery in 3 days. Perhaps you and she could meet with a nutrionist while she is in hospital?