If she is concerned about her periods, she should go to the doctor who prescribed her the pills and ask. Medical advice like this shouldn't be given only through the Internet., and I say this from personal experience. A month ago I got some abdominal pain (it wasn't there all the time, just every once in a while) and almost didn't go to the doctor to get it checked out. It turned out to be an ovarian cyst, which wouldn't have killed me but it was good to know so I could heal faster knowing what the problem was. So in my opinion, if your girlfriend feels like something might be wrong she should ask her doctor. (In the US, you can just call the pharmacist and ask but I don't know if you can do that in Denmark) Hope all works out :)
