I need to break away from this friendship, but how?

We have been friends for almost 3 years now and have lots of things in common. We can talk for hours and she is my only close friend these days. The problem is I find her extremely self involved and i know that she perceives herself to be better than me in many regards and sometimes this is very obvious even though she thinks i am not aware. you name it, intellect, looks, style, taste in music, sh eis better in all those and more.... Being with her is starting to send me into a depression. Its like talking to someone and revealing your most private secrets to a person you don't actually like. Sometimes i catch myself thinking, that she is the person i hate the most and love the most. "love" her because we can talk about many things and she always knows what i mean, i havent found that kind of understanding with anyone before. her personality however i do not like. She is a self proclaimed *****, not the kind that will curse people out and be loud and ridiculous, she likes to think she is a more high cl *****...I think she fancies herself to be some sort of female version of Dr House where she is capable of playing with the "little minds" that most people have. I find this extremely conceited and deluded, I cannot stand it. I want a close friendship, but with someone that i can actually grow from, someone with something positive to give.