If she doesn't like him, she doesn't like him. The reason why she told him she like someone else because she know OP liked her but she didn't feel the same way. It is easier to say that she liked someone else (which is probably the truth) than to say, "I don't like you".
OP your friend is being a douche about this. It is unwritten Man Law that one man will not interfere with another man's pursuit of a girl. But did your friend know of your intentions? If he did, you better talk to him and ask him to be honest and see if he likes her. If he does, back off, he has a better chance than you, if he doesn't ask him to help you out. If he didn't know about your feelings toward the girl then it is your fault for not letting him know.