What should I do if she won't agree with me?

My best friend and I have made plans to play badminton and go to the gym this summer so we can get into shape. But I want something more. I want to learn how to play soccer, but just the training in the summer. I told my best friend, and she keeps going against it. She keeps saying that it's not my thing, and all my enemies ( people who don't like me) play that sport and I might end up being one of 'them'. I really want to, because I want to try something new. I know it's going to be hard work, I really want to try it. But my best friend doesn't agree and saying we won't have time to hang out. Should I risk my friendship with her and do it? Or should I just not go for what I want? please help!!