What does it mean when a girl tells me she likes me but we cant date and then dates with my friend

this girl that I like talks to me everyday and she constantly tells me that she likes me but she is going out with my best friend. what should I do??

Sounds like you and the girl may have different definitions of the word, "like." There's nothing you can do to make someone date you when they don't want to. I'd move on to another girl.