Sounds like Endometrosis or Cysts. I had some cysts in 7th grade and I am now 31. Lost an ovary to a chocolate cyst, so I have endometriosis now and must have my birth control taken for two months without a period to put off the endo.
You may think about putting her on BC and that sometimes will help with the symptoms of PMS and endo (if that in fact is it). You may end up having to monitor it very closely as it also could be that your daughter is sexually active and has gotten an STD or even the new thing that governer of Texas wanted girls to get vaccinated against.. some diesease.
Sorry to hear she is hurting.. in the mean-time, go out and buy some midol, that can at least allow her to have less pain.
She sounds exactly like me when I was younger. My sister whom is 17 has the same exact problems..
Wish you luck.