I have been celiac for a number of years, it sounds frightening, but the surgery could be to remove damaged intestine or bowel, it is pretty routine these days. gluten free diet is not that difficult to follow either once you learn about alternative flours. rice flour is great for swapping gram for gram in things like fatless sponge cake and dumplings. For batter e.g. pancakes, battering fish etc. replace gram for gram wheat flour with rice flour and add a little baking powder and xanthan gum powder to make it lighter. mix rice flour, xanthan gum powder, baking powder and enough water to make a dough, this can be rolled out or flattened into a little oil in a hot frying pan/skillet and cooked till golden on both sides to form a kind of very quick easy bread, great with soup, to make breadcrumbs or croutons, and if made thickish it can be sliced in half to make sandwiches.
the difficulty will come with hidden glutens, gluten is often used to stop things sticking together in processing and packaging stages e.g. some dried fruit, some baking powders etc. it is also used as a thickener, soups, gravies etc and as a crisper on oven chips to name a few. best way it to prepare everything from scratch(raw ingredients) that way she will know exactly what she puts in them.
good luck to her x