Reposted this guys, big arguement..?

Well. I'm 14 years of age, just started year 10 in comprehensive. I always seem to argue with this one girl who used to be my friend, she constantly lies and argues with me, even over the smallest things. She used this social networking site to hook up with this boy. She arranged to meet him one day and the boy brought his mate (lets call him Tom). She then asked if I fancied meeting Tom to see if I would like him. I met him. We were both very shy the first day we met and just didn't speak a word and just kept smiling at eachother. He then came up to meet me on his own one day and asked me to be his girlfriend. He then finished with me 2 months later because the distance really affected our relationship, then the girls boyfriend finished with her two weeks later. She then started arguing with me because I kept talking to the boy who finished with her but obvioussly we were just talking as friends, she thought different and stabbed me in the back to other people (more or less saying i was a tart and a slag) never talked to her since. She's now made a fake facebook account to spy on me and the boy. Obsessive or what?! I never wanna be her friend again, this isnt the first time we've had a mive row like this. What should i do to avoid anymore arguements and stay out of her way?