Has she been tested for H. Pylori? It's very important that she has not been on any antibiotic or peptobismal for one month prior to that type of blood test, amongs a few other drugs weeks prior to testing, as you won't get an accurate read.
My niece was having similar issues, went through many tests etc...and it continued to get worse for her. Until she started crying and moaning in pain at night as well...I told my sister have her tested for H. Pylori..she indeed did have H. Pylori and was treated for it. She started doing better with going back to school as well. I hope whatever is going on, you two can weather it. It's difficult, and she's coming to that age for "girls" that womenly changes start happening, so she may just be having some nasty old mood swings. The premenstruating times that young ladies go through for up to a year or more before getting their periods. argh!!! hugs, Lisa