My girlfriend has been acting very moody...what can i do to not bug her or to cope with the situation?

My gf is a wonderful girl. About a month ago we tried dating but she broke up with me due to her being confused and stressed with stuff and her friends being idiots toward her and giving her a lot of sh!t. then last week i asked her out again and she accepted and things have been going great...then a few days ago (esp yesterday and the day before) she has been acting EXTREMELY p'od. so i am assuming its pms considering it seems to be monthly. if it is when should it blow over and how should i deal with this? i really love her and i dont want to lose her.