I hate my friend but don't know how to end the friendship?

I feel my friend is manipulative and emotionally abusive. Every time I encounter her and we interact she verbally assaults me , or she'll be having a discussion with another individual and talk bad and/or down to me. She's even threatened to physically assault me in one of the instances I'd stood up for myself. After the last straw has finally been reached, I'd decided I no longer wanted to but up with her bs and decided she didn't deserve an explanation - I'd just ignore her. When she noticed this she then proceeded to act as though she cared about me. She tried to weasel information out of me about my depression to use against me and tried to convince me that she is really my friend and I even broke down in tears even though I knew it was all a lie. But whenever I'm around her she always belittles me and puts me down and acts as though she really does not care about me and often encourages her other friends to treat me the same way. Throughout my interactions with her on several occasions she's referred to me as being a little intelligence and not a very strong person even though my grades are just as good as her's are and she's never even seen me do anything physically. I'm absolutely sure that it goes without saying that she believes that I am mentally weak as I not only am a quiet person and she notices this but she also keeps trying to weasel me back into this friendship and I'm pretty sure she doesn't think I'm onto her. Throughout the 2 1/2 years that I've known her it's become very evident that she looks down on me and only sees me as a plaything how do I out right tell her that I no longer want to be associated with her?