I'm mad at the way my girlfriend dresses
Why don't you like the way she dresses?
I don't like when she wears tight clothes or short skirts.
I hear you, but you not liking it does not make her clothing choices wrong or bad. Rather than her changing what she wears, I'd advise that you ponder why you don't like it.
She should be listening to me since I am the man.
I respectfully say that you are wrong. You being a man isn't a reason for you dictating how another person, especially your partner, should dress. I'd suggest doing a bit of research about gender roles and how many of them of dated and misguided. She's probably dressing in a way that makes her feel good and confident and that's a thing that should be celebrated and supported.