There isn't sufficient information to reach a specific diagnosis. I would advise you to take your gf to the ER so that she can be examined and undergo investigations such as urine analysis, ultrasound(if indicated after examination), etc to find the underlying cause and have it treated accordingly. She will require a painkiller to reduce the pain for now, you can also apply a hot water bag over the abdomen for 10-15 mins and then massaging the abdomen gently which may give some relief.