I Have A Friend Who Is A 19yr Old Female.

I have a friend who is a 19yr old female. She has had surgery in the past year for a hernia. She has frequent pain in her belly button and wakes up ever morning and vomits. she is not pregnant, does not drink or take drugs. the pain is so severe sometimes that she has to miss work. any ideas? She has been to the doctor but they can't seem to pinpoint the cause.