<human>: Can you condense the text into three sentences or less?

Hi all. So, basically, I love my girlfriend. We've been together 4 years now. She is sweet and kind and super cute, and we have a lot of fun together, but she can also be very snippy, short-tempered, self-absorbed, complainy, stubborn, and mean, especially during the week before and during her period (but also the rest of the time.) Colloquially, this is called being a bitch. Whenever I try to bring it up though (and I obviously am not calling her a "bitch"...that would be crazy), it gets WAY worse, and always causes the worst fights. 

Any advice on how to approach this? Any techniques maybe that I could share with her to help her be more easy-going and less sensitive? I love her and I am not looking to end our relationship or anything like that. I just want her to be more the version of herself that I love, and less the Mr. Hyde crazy she-monster. And I know that she also wants to make me happy. But for whatever reason, She's just sort of a bitch. 

Maybe any advice on how to help soothe PMS etc? I think maybe this could be part of why she is so on edge all the time. But, of course as soon as the syllables "P M S" leave my mouth, she goes off. I'm not going to make that mistake again, so covert techniques are best. Like to help calm her PMS without her knowing. Or maybe code-words/euphemisms that I could use to get the conversation going without setting her off.

Really, anything you can offer me is appreciated.
<bot>: I love my girlfriend of 4 years, but she is a bitch to me often. How can I help her not be a bitch (as much)?