ARG help with an obnoxious sister?

I would say try spending more time at your friends houses. She can't go there with you. Try listening to music she won't like. Wear clothes she won't. Ask her what she likes and make suggestions. Like say "I think it would look really cute if you wore that pink sweater with those green jeans", which gives her fresh new ideas. In the meantime it also will make her think of other things she can do that you might think are cool. Then she's doing her own thing, but she knows you think it is cool. That's all she really wants. Your approval and acceptance.