Advise on gallstone

My fiancee found out in janaury that she had gallstones, shes been told to limit herself to 3 grams of fat per 100 grams, shes had about 6-7 bad attacks since end of January and the last one was so bad it apparently affected her pancreas and was told she had to admit to hospital for a few days. Anyways she went back again and was told that the problem with her pancreas had cleared up. Since then she has been eating more fatty foods like cheese butter mince and so on. She hasn't had an attack yet and she thinks that the stones might have passed. Is this possible? She's also been told by NHS that its atleast a 2+ years wait for keyhole removal or the whole thing removed.