What do girls do, think, and go through when they likes a guy and want the guy to like them/her in return?

recently, I met this girl. I think she likes me, but I don't think I have the same felling toward her. She has been inviting me to a few events, I went. But I didn't go roller skate with her tonight and the event was canceled. She never expressed that she likes me. Should I ume that she likes me? And should I make it clear that I only like her as a friend? Help!!