Am I being selfish, my friend says I am?

I want to change schools next year and my best friend said she would replace me if I did and that I was being a horrible friend for doing this. It really upsets me that she won't support my choice because I know it won't be easy. She said I was stupid and had no real reason to change, but she doesn't even know why. I want the chance to start over and be a more out going and likable person, all of my friends at our current school are mutual friends with her to and all of them pout her ahead of me, I am tired of her always being better than me and everyone liking her more. I just want to meet some frikin people who don't know her and are actually friends with me for me, not her. I told her I was thinking about moving in with my dad to and she said she was going to stop talking to me and wouldn't be my friend anymore. Am I being selfish for wanting change and not having a good reason? I never see her at school anyways so I didn't think it would be such an issue to be honest...