I'm writing a book...?

You should maybe try the psychology section, more people will probably be able to help you there. Also, you should write about the pro-ana websites that anorexics often go on (they post pictures of 'thinspiration' celebrities and photos of themselves, and they encourage each other to stay anorexic. They're awful websites, but a lot of anorexics do go onto them, so your character probably would.