What Causes Severe Abdominal Pain And Vomiting?

My daughter is 19. She has been to the ER 5 times in the last 6 months with severe abdominal pain that builds to a 10 until she starts vomiting, the most recent visit was yesterday. She vomits 12-16 times over about 3 hours. She gets temporary relief when she vomits. She had an abdominal CT Scan in October and again yesterday showing PanColitis. She followed up with a GI doctor as recommend after her second ER visit. All the following tests have been done when she is not symptomatic due to scheduling the follow up process and come out normal Endoscopy and Colonoscopy with biopsies on 11/27/2017 abdominal ultrasound end of January, Abdominal MRI mid February. Allergy testing at PCP showed nothing either. She has been in the ER twice since last seeing the GI doctor and has an appointment later today. Any advice on what questions to ask or information that might be relevant? Any experience with these symptoms that may shed some light on what we are looking for?