Dear Mynameisheart,
You still too young to understand that everybody do not think like you do or talk like you. Am sure she doesn't hate you, BUT she just doesn't want to be friends with you, let alone being a future "Girlfriend". Am sure you are a nice guy.
You seem confused and just want to know "Y". Sometimes in life, one will never get to know the answers to all the Y's during our lives here on earth. But at the end it will be Your own decision either to move past the Why and move on with your life, because nobody is going to do that for you, except you yourself.
But, try to to understand when someone doesn't want you, to be their friend or if they are not attracted to you. Just respect your self and move on with dignity. When you persist in wanting to be with them or around them regardless of all the signals they have given you, that is when they start seeing you as creepy. And that would really make them even dislike you the more, because You just don't get it!
I believe God did not put her in your mind or in your heart, but YOU are the one who just can't control your own feelings. Get your self busy, stay away from her and her brother if possible for a while, try make new friends.
Am sure she will start respecting you ONLY if you can just stay away from her and her group of friends if possible.
There was a situation where i didn't like this guy and i was not attracted to him. But he probably was into me. First, i didn't respond to his mail, because i know he wouldn't take NO for an answer. But somehow i was hoping he gets the signal of me not responding to him means am not into him. But, he didn't. He contacted me again the second time, i didn't respond. The third time he did, i wrote him saying "Why are you so dumb to get it that am not into you". Then the last time, i just Block him!. If he had respected me the first, by not sending more mails, i might probably have consider dating him in the future or having him as a friend or even not at all.
Is not everybody i like and admire that is going to like me back. That's life, deal with it!