My 'friend' lies about everything?

I have this 'friend'. We've been friends since we were 6. She lies about the most ridiculous and small things that aren't worth lying about. I think she lies to make herself seem better than others, and to make her feel better about herself. For example, we were running laps and we had to run as far as we could in 20 minutes. She said to me "How many did you get?" so I said "22, and you?" and she answered "Oh, 23." I remember lapping her. I took my cactus into school for a project and it was in a bag. She put her hand in, I saw that it didn't touch the cactus, and she took it out and screamed. She even told my other friend that she 'puts on an act.' And it's not just the lying. She is so pretty and she acts really sweet and cute in front of the teachers, but she hurts me and my friends, like physically. She was begging me to tell her a secret and I kept on denying, and then she said "You can trust me, I'm the priest's daughter." I wanted to scream at her when she said that. I spent ages on my homework and she wanted to copy, but I said no. Then she said "But I'm dyslexic and dyspraxic, so you have to let me." She is so touchy feely, she even tries to give us love-bites and when we tell her to stop because we find it gross, she gets upset and annoyed at us. I don't know how to deal with her anymore, every day I have to pretend to like her, because I would feel terrible if I told her that I didn't want to be her friend, but it's really getting me down. Every day I come home from school and I just breathe deeply and try to forget about her. Sometimes I cry because it puts me under pressure and makes me feel depressed. How should I deal with her?