Ok i don’t know too much about this in terms of medication etc but the other halfs twin brother has it.
He was late 20s when diagnosed, they thought it was his apendix till they went to take them out and had to remove 1/3 of his stomach.
He seems to control it mainly by diet and drinks Yakult (sp) to help his digestion. He tries to avoid food that is high in fiber and carbs like bread, potatoes pasta and rice and sticks mainly to white meat, fish, veg, pulses and fruit.
He is under a consultant for regular check ups and doesn’t seem to have much in the way of problems although i do know of other people who have had other different experences with Crohns.
Good luck to your girlfriend with this and tell her to follow her consultants advice & she should be fine.