I have a friend 'Emily' who has recently told me that she's bulimic. She tells me she sets a target for her waist size and once she gets to that she sets a new smaller one. It's like she's never good enough. Right now she's less that a 25 waist with a BMI of 17.

Her grandmother 'Mary' is my neighbor (it's how I know Emily) and I'm wondering how and even if I should tell Mary, because I don't know how to get a hold of her parents and I don't think I can talk her into stopping.

Emily is a nice girl and I don't want anything bad happening to her. I need help here.