I think some aspects of an ED may be labeled as compulsive (like purging or over-exercising), but I personally view them more as a coping mechanism.

Is there some driving force that is causing your daughter to criticize her body in such a way? Is she with friends who are reinforcing her behaviors? Could anyone be making fun of her at school? Or is there something emotional occuring in her life that she doesn't know how to handle?

You're doing the right thing by telling her how beautiful she is. I would actually encourage it to the point of annoyance, because that's probably the only way she's going to get it in her head. If she hears it enough, maybe she'll start believing it.

I would definitely keep a close watch on her eating patterns and any "behaviors." Some of them may be cutting up food in small portions, frequent trips to the bathroom, drinking an abnormally large amount of water with her meals, chewing gum constantly, etc.

While watching out for her, overall I'd strongly tell you to look her straight in the eye everyday, telling her how beautiful she is and how much you love her.