What Causes Delay In Menstruation Other Than Pregnancy?

my girlfriend is 16 years old with a one year old child. she has missed her period going on two months now but isent pregnant. she has bad cramping pains as if she where having a period. they tested her to see if an egg was in her tube but no. and now they want to test her for overian cancer. what is the chance she could have this? and is it likley fatal?