Does she envy me, or is it that i'm such a bitch?

I met this girl when I was a 7 grader. I used to be a more to the lonely side, but she just came and hang around with me. I don't know what drives her to, but she just did.
We both became close and we spend more time with each other than with any other else. She would laugh at my jokes, and hear what I have to say. She was the sweet girl everyone see as nice and polite; the princess like girl who appears so sweet and innocent
We compete academically (She took the third rank while I got the second) and we're still fine with it.
But lately, things get more different. After we had a debate about our beliefs, she began to change. She began to disagree at everything I said, and she began to be more competitive.
If I punched the wall once when I got angry with this shitty boy I hate, she'll say she trained her fist by punching the wall of her room, and punch random things at school since then.
If I asked a more mature friend about her opinion about a part time job (coz I really need money) she'll show up on chat room and ask me how to earn money (She said she needed money to buy an i-pad), adding note "I don't know why converse to you about this..."
If I prove myself to be more practical in science (She's better in theory) she will look at me with that contempt look on her face.
If I went and join the school basket training, she'll show up and said "Stop copying me."
And whenever I look at her for a moment too long, she'll give me a contempt look.
Of course, i get the message that she doesn't like me anymore, and i started hanging out with some other friends.
She once stated that "I wanted to laugh on your face." Well, she tried (I heard her forced laughter) but I told her, it wouldn't affect me, and again she gave me that look.
Few days later, I tried to asked her if she really hate me, by pressing her on to get angry at me (People can blurt the truth when they get angry, that's what I tried to applied). But she just asked me, "How do you deal with selfish people?"
And I don't need a sixth sense to know on who she meant.
We both rarely talk now (Who can stand her sarcastic comment?), and I hang out with the others. She would stay by the sideline, and watched me with that contempt look. I wouldn't care less, if she didn't tried until now, to laugh at my face. I stayed away from her as far as I could get. But she started to get close to the friends I hang out with. Why couldn't she hang out with another?!!
She's getting on my nerve, now people, lemme ask you, is SHE normal, or not?!

Note; I would appreciate if you would give me a suggestion on how to deal with her, but you can't suggest me to go talk and straightened things with her. She's hopeless; she would say that there's nothing wrong and wouldn't admit how she felt for me. (I know how she felt for me coz of her expressions). She would act the innoncent girl, and give me that forced laughter of hers...