Originally Posted by ~Tortured Beauty~
If she is making herself ill after eating then she is more likely to be suffering from Bulimia Nervosa, rather than Anorexia Nervosa.
Try telling your mum that you are worried about your sister but are not sure exactly what is wrong. That way you don't appear to be jumping to conclusions, simply expressing concern.
I agree with Carole. You should tell your mom. Also, please don't use excessively large font when posting, thanks!