Yeah, you're right. I don't understand.

So I was talking to my friend the other day. This is his situation.

He likes this girl and he talked to her for a couple weeks. Everything was going smoothly. She's really friendly and is an easy person to talk to. Getting subtle hints, he decides to take her to an ice cream parlor to hang out. For some dumb reason, he thought it would be a good idea to ask her to prom. The girl says no. She gives a list of excuses but in the end, my friend still got rejected.

So now he asks me what he should do.

I said, she was probably just nice to you because that's just the way she is. She saw you as just a friend. What you should do now is continue to talk to her and give subtle hints. If she gives you short answers and it seems like she's ignoring you, that means she's not interested and she doesn't want to lead you on.
BUT if she continues to talk to you in a friendly way even though she knows you like her, well that either means she likes you back or she's being a jerk and is leading you on purposely.

Did I give him good advice?

Right now, I would hate to believe that girls would purposely lead guys on when they have no interest in them even though the girls know that the guy likes them. You know?