You might try going through the "eating disorders, addiction, and self-harm thread"
http://www.gaiaonline.com/guilds/viewtopic.php?t=633122While I haven't had anorexia, one of my friends was becoming increasingly close to this disorder a few years ago, so I know how scary it is to watch some one going through this.
Stay strong, be there for your friend if she needs some one to talk to. If you feel that you yourself need some one to talk to about her situation, try you family, other friends, or a teacher/consuelor, or even some one here online. Though I would go to people you know better first.