How to know everything about her period?

I need info about my girlfriends period. She has huge mood swings sometimes,and sometimes she gets real horny. I dont want to ask her,because that might raise questions.

But i know the date when she started having birth controll pills. Can anyone tell me about monthly cycles girl has?How they feel Before period,on period,and after. I just want to keep track on that so i can cope with her moods. Thanks for any info!