Being a fan of her figure can kick-start her confidence, but she'll have to take it from there. She says she just gets emotional sometimes, and that everything irritates her. There is no rhyme or reason to what will peeve your girlfriend during the week before her period, because the evil hormones causing her wild mood swings know no logic. Maybe I'm a little biased here, but I strongly feel you should stick around and put up with it. Cut your woman some slack by staying by her side and letting her nastiness roll off of you like raindrops on a weatherproofed deck.
Most women only experience premenstrual symptoms for a few days.
Unless she comes right out and requests alone time, she probably prefers to have your company. It's the area halfway between her armpit and hip on the sides of her torso. While you're kissing her, put your hands on her waist, then slide them up to this part of her body, just barely brushing the side of her breasts as you do it. You'll be turning her on without really making a move, which is perfect for a first or second date situation. There's something about that almost-touch that makes us kind of crazy.