My best friend seems to think that I like the person she has a crush on. But I don't like him. How to clear her mind?

If you have someone you like, talk to your best friend about the person you like and let her know that you don't like the same person. If you don't like someone for a while, talk to her more about what kind of person you like, and be sure to be different from her. That's what I used to do.