When the kidneys form, they do so further down in the pelvic region. As the body continues to mature prenataly, they ascend into the position that they occupy post birth. I don't know the exact incidence of this, but I believe it isn't hugely uncommon for the kidneys to end up in a different location due to improper ascention (they can get caught up on different blood vessels, etc.). The specialist will be able to tell you whether their location is an issue or if there are any other concerns with the scan.
What your girlfriend may be having is called ectopic kidney. An ectopic kidney is a birth defect in which a kidney is located in an abnormal position. Mostly ectopic kidney do not pose any problem but if the kidney is enlarged then polycystic kidney needs to be ruled out.
It is a hereditary disease in which a large number of cysts grow within the kidney.
I suggest your girlfriend to consult a urologist for immediate review and further investigations.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.