I hate my girlfriends fashion sense

It's to a point where I feel embarrassed to be out with her. I don't even know where she gets these ideas from. Long denim jean dress with weird patterned socks and ballet shoes? She didn't dress like this at the beginning of the relationship but now a year in she has changed. I'm just a plain t shirt, shorts and tennis shoes. Would like someone who dresses more plainly. I'm surprising by myself that something like this is bothering me so much and don't mind if it's a random stranger like this but for some reason I am finding in a relationship it's coming out. Something wrong with me?