Mostly for the girls - Help with PMS?

A'ight now, I love my girlfriend very much. I think she's perfect in pretty much every way. I tell her that all the time. We're just devoted to each other. However, one thing really gets to her. PMS. Every month, she is a different mood. She gets mad at me for nothing. Also, she's had a really tough life, like family problems, deaths and abuse. So I guess she has a reason to feel like "I'm so unlucky". Now like I said, I love her so much, and I know it's all about a little l discharge. But is there anything I can say or do to help calm her mood? Thanks very much.