I think my little sister thinks its cool to have an eating disorder. Should I tell mom?

Yes, If you believe your sister has an eating disorder, please do discuss this with your mother, i know that your sister may not think you are doing her a favor, but later- i hope she does. In certain cases eating disorders are life-threatening. I know you would deeply regret not trying to get her help.If your mother does not take action for any reason, tell another close adult; school nurse, counselor.