Iinl to still have feelings for someone you at the same time hate?

So I've known this girl for a while. I did really like her, so I asked her to prom. She complained about "Oh, my feet hurt" and even complained about our freaking limo. Of course later on I saw her dancing with other people and she was talking to me about how she was planning to go on a date after prom! I know, wtf. But, I did have a good time because a lot of my friends were there and they didn't let her get me down :) So I haven't talked to her since until she posts on my facebook and drives past my house. Now those feelings before prom are coming back while on the other hand I still hate her guts. Is this normal or am I just a psycho?