What is causing my fiance's reoccurring pain and diarrhea after he Gallbladder was removed 2 years ago?

My 27 year old fiance has chronic abdominal pain and diarrhea 10-15 minutes after eating. Some of the time it is infrequent but lately every single thing she has eaten has given her these symptoms. She does not eat fatty foods, drink soda, eat spicy foods or drink. She has eater whole grain food, high fiber foods, vegetables, fruits and nearly every other recommended food. All of these foods have triggered the pain and diarrhea. She cannot seem to eat anything that will not effect her. I am not sure if it is because without her gallbladder to store the excess bile it is being released in too great of quantities. I am getting worried that she is getting malnourished. For the past week she has been having these symptoms even without eating.