Extremely Abnormal Period (6 month without!)

My roomate has a very very weird period.
She went 6 moths without one. She's had I think 2 periods since the start of the year.
She's been cramping for about two weeks now, but no period.
I'm suspicious that she may be pregnant. She is sexually active.
I keep urging her to see a gyno, but she hasn't gone.
Her mother says "it's normal" because she was like that when she was younger.
I don't buy it.
She said the eggs might be turning into cysts every time she misses a period.
What is that called? Can it be dangerous?
I know you guys aren't docotors, but I was wondering if anyone has had experience with this and/or any knowledge about it.
thanks!
L