I'm mad at my girlfriend for getting her hair done on our anniversary
Why would getting her hair done make you so upset?
I try to think about her but I like her beauty the way she is, that's why I get so angry.
That is pretty controlling of you of you. It's wrong to be mad at your partner for reasons like that. She likes to look good and feel good so you shouldn't fault her for that.
She is pissing me off.
That's really not a good reason to get upset.  What you're engaging in right now is some pretty controlling behavior and continuing to act in such a way could harm your relationship!