How can I stop her from teasing me?

Note: This situation is very serious for me. So please, I only want answers that makes sense and would answer my question. 10 points for best answer :]

School just started this Monday - June 8, and there's this new guy. Yesterday, he was asked if he could work alone on our upcoming experiment. He immediately laughed and everyone laughed as well because he looked very funny when he laughed.

When class was over, I hung out with my best friend and talked about our past classmates. Our topic normally shifted and we both remembered at the same time how the new guy laughed. I told her I only laughed because his face looked funny and that it looked cute too.

Ever since I said that, she's been bugging me that I like him even though I really don't. She's been screaming his name just to tease me, and I feel very very very awkward since my past classmates were around and they might make a rumor out of it.

So.. How can I prove to my best friend that I really don't like him? She's the type of person that would love teasing people even if your her friend. I'm really irritated because of what she's doing.