I guess some people never grow up huh? You need to block any contact you are getting from her. You can block any emails or facebook/bebo/myspace details and also block her number from your mobile/home ph. Also tell your friends you dont want to hear any gossip either, that way she wont be able to effect you. You may still hear the odd thing but mostly in a short time it'll all become to hard for it/her to get to you. And what you dont know wont hurt!
Unless your life is being threatened...that would be a whole different story!