Have they checked for a kidney infection? I had similar symptoms from a kidney infection. Good luck and I hope your drs figure it out soon.
Your girlfriend needs to see another doctor asap. This could really be anything. The pains are most likley associated with the menstrual cycle....which is why she only has one every 4 months or so. I would suspect PCOS or possibly endometriosis. I would say for her, that she needs some more blood work....and an internal/external ultrasound. Here is a list below, if PCOS is supsected, here are some of the hormones that need to be tested:
Lutenizing hormone (LH)
Follicle-stimulating hormone (FSH)
Total and Free Testosterone
Dehydroepiandrosterone sulfate (DHEAS)
Other hormones that may be checked include:
thyroid stimulating hormone (TSH)
In addition, glucose, cholesterol (HDL, LDL and triglicerides) levels might also be assessed.
She needs to address this issue asap, so no pernament damage occures.