What percent of girls who start dieting at 13 end up with eating disorders?

I know a girl who has been dieting since she was 13 and still is (she's probably around 15 now). What are the chances of her getting an eating disorder? I've heard that like 86% of girls who diet at that age end up with one, is that true? What statistics do you have/know? I really would like to warn her parents, especially since they see nothing wrong with her behavior. I'm not sure if she's throwing up in a bathroom or anything like that, but she definately is watching what she is eating, eating foods marked "low carb", keeping track of how many pounds she has lost, and exercises for the benefit of weight loss. Also looks like she could use a vitamin if you know what I mean..
Thanks to all who help.

chances are she probably has one she may not meet the qualifications for anorexia or bulimia but she could be EDNOS (eating disorder not otherwise specified) which can become much more serious and turn into anorexia or bulimia . if you have an eating disorder you dont have to be underweight everyone has to start somewhere right? if she looks like she could us a vitamin id suggest asking her how many calories daily she averaging if she hesitates to answer then shes probably going to lie to make you think shes eating a regular amount if she says 1200 or 1500 she probably actually means 500-800 , telling her parents wont help a lot of adults dont understand it your friend should prbly get therapy or you could get her to talk to you and maybe even eat out with her make sure shes eating ATLEAST 1500 a day a 13 year old girl should be eating 2000 but if your friend has an eating disorder eating more then 1500 would make her freak out and when people with eating disorders freak out then they turn to puking.....i could keep going and goin and going but im gonna stop now

80%, who knows? not me.