N.K.
Is she underweight? I had a co-worker who was underweight and she'd get her period about once a year, if that. She said that when she was a teen, she never got it, and then when she eventually did get it, she'd get it about once or twice a year. She was underweight (about 85 lbs. or so), and may have been anorexic, though she didn't disclose that to me. When she wanted to get pregnant, she had a lot of difficulty because of this anomaly with her reproductive system. She put on some weight and slowly, her reproductive system started to normalize and her periods became more regular.