What Could Cause Missed Periods, Abdominal Pain, Loss Of Appetite, Dizziness, And Nausea In A Woman With PCOS?

My girlfriend has not seen her period since January. This happens sometimes as she has the condition PCOS. Just to be sure we took a pregnancy test on the 3rd of April and the results were negative. Yesterday and today she has had sharp pains in her abdomen. This is followed by a feeling of loss of appetite, dizzy nauseous feeling and the feeling of want to throw up. What is going on with her? Please help