I would have her checked for Celiac Disease (CD)... I have something VERY similar.. But I have had it for 6 years. I was diagnosed 1 1/2 years ago with CD. And since then, with a TON of research, I have found others with severe lower right abdominal / hip pain...
I have not yet found out how to help it.. I was also told it was all in my head and I was faking it (it started at the age of 15, I am now 21)..It went away in early 2007, returned in January of 2010. It is so severe I usually can't do much of anything. It feels to me like being hit by a semi with knives on the end.
BUT! Good news.
I go to a chiropractor. They do NOT crack my neck to align my spine, they use a type of machine. ((I am not certain as to the type of machine, and you will have to find someone who uses it.. I will get the name from my Dr. as I am not allowed to post the office's contact information on here.)) I have my spine aligned, and after a while, it does TEMPORARILY relieve the pain. But ONLY A LITTLE.
You could also just try your daughter on the Gluten-Free diet to see if it helps her feel any better. She could be a Celiac.
Rebecca