A Sign of Rebellion _ It's a way to reject gender expectations and show that not only guys can have short hair. Some girls do it to express themselves in a way that says, "I'm different and I don't care what you think!"
Being A Mom _ Some women say that being a mom is a great cause for going for a shorter look. With a new baby it's hard to find time to keep up on looks. It could also be due to the fact that children love to pull on and rip out longer hair. Going short solves that problem.