I'm pulling away... Is this a right move?

I think i have a condescending friend or something along similar lines... These are the symptoms;

- She calls me stupid and dumb and never apoligises.

- She has been gradually getting more confident and cheerful since conveying her dis respectful behavior towards me.Note that while she's going up in mood i'm going down in happiness.

- She apologises to others for her mistakes but never apologises to me.

- She demands a justification for EVERYTHING I do

"Why are you in a hurry?"

"Why are you intent on doing something active this semester?"

"Why do you want to get that one and not this one?"

- She studies and examines my every move, emotion and look. She stares at my writing when I write and demands and pesters to see my artwork, which i'm not comfortable sharing with her, or anyone anymore.

- If i beat her in a web game she'll brush it off and say "yeah yeah yeah, whatever i know".

What do you think is/are her intention(s)? I've been feeling upset and down lately, i just don't enjoy her presence anymore. She's in alot of my classes next year, and i want to avoid her and find new friends. Even though i've been giving her a sort of cold shoulder she continues to follow me around and chit chat. I can't stand it, she's been robbing me of my happiness, and i haven't been reacting well. I have been backchatting her and falling back in frustration because i can't understand...

PLEASE HELP.