my best worst friend

I have bean best friends with my classmate since before we could attend elementary. Even in our younger years she consistently bashed every bit of confidence i have ever had straight to the ground. I didn''t notice it then, but now...it's a million times worse. She picks apart every thing i do, disses my family members worse than me, tells me all my flaws, and even goes as far as to make it a public activity to attack my face to try and pop a zit!!! I have told her to back off and for a moment, it seems to work, but it starts up again only 10 times worse. I have zero self-respect and confidence and i know it is a result of her constint bitchiness over the years. She never has apoligized to me, never has their been a time where we get along great and nothing she does hurts me. I am just trying to wait it out until the end of senior year (2 years from now) until i am fully done with her. We live in a town of 1000 people so i don't really have any other choices than to keep her around. I have other friends but their all her friends also, and it's better to be on someone who's that lethials' good side than on her bad side isnt it? I feel like im talking to a bumerang every time im near her, if i say something bad about myself aren't friends supposed to say "oh, don't say that! your fine!" instead she says..."omg! your nose is huge!", that is just many of her nitpicks. She also always goes out of her way to make it seam like i fart all the time, we will be standing there and all of the sudden, "OMGOMGOMG! You FARTED...gross" and she always does it when guys are around! She especially likes to bash my smile, so i have recently kinda quit smiling just out of habit...i was in the hallway and one of my friends gave me a gift for my birthday..so of course..i walked into class smiling..guess what she said.."GOD! why do you have that look on your face, it looks like your constipated"..i probably havent smiled since. Even as i am typing this, i fin myself thinking..why am i still friends with her..if i were reading this from a different spot i would be so incredibly confused as to why the people in this little novel are still in the same loop. I know i should break it off, but i can't, it would be the weirdest thing ever!Oh man..if she ever knew i wrote this...i hope i wouldn't be alive the day got hands on it...