Stomach cramps passing out?

Hi everyone. A friend of mine has a problem I am hoping we may be able to shed some light on here. I am reposting from her Facebook post. My young daughter has been having belly cramps for over two weeks now and pains in her chest...then sunday morning she woke up with diarrhea and I heard her scream like she had never ever before...ran to the kitchen and she screaming she could not see, (the pupils in her eyes were all the way dilated) I grabbed her up and she went limp on me (passed out) she had never done that before...they did E.K.G , blood work, xrays,and a cat scan of her brain..everything is coming back negative.......anyone have any suggestions? Thanks for your input