Do I have to tell her that I like her?

Hi, I'm 18 years old guy. So... I study I in college. There is one smokin' hot girl in my cl. She is 19. I think I like her (not falling in love). But she has a boyfriend. Then do I need to tell her that I like her? I'm so confused. I know I don't have a chance on her cuz she has bf. I just want to see your opinions guys! Thanks :)