My cousin and I keep fighting, WHY?!?!?

I don't like my cousin either and were around the same age. Tried to hang out with her for a while but she seems too.. "junior-high" like for me when she's supposed to be acting like a 17 year old. I'm 19 by the way. My solution is, I don't interact much with her. I have my own friends and she has hers. Just because she's family, doesn't mean I have to like her or hang out with her let alone please her.