Why can't I get a short haircut, just because I'm a girl?

Recently, I was at Walmart talking to my dad about how I want a short "boy" haircut. He went to the hair salon that was in the store and told me I could get my hair cut. I called my mom to see if I could do it and she said no, because I am a girl. I want to get at least 100 signatures on this to show my mom that girls can have "boy" haircuts. Then hopefully I can get mine cut.