I'm Worried About My Friend?

[Sophie]

Me And My Friend Are Both 15 And Want To Lose Weight. I'm Just Cutting Down On Calories And Exercising More, But She Is Going Over The Top And Not Eating Any Meals Whatsover And Telling Me If She Does Eat Something She Will Make Herself Sick Straight After (Bulimia) And She is Currently Having A Week Off School Claiming That She Doesn't Feel Well. She Isn't Keeping This To herself Either She Is Telling Everyone 'OMG I Havn't Had Anything To Eat In Like Three days' Sounding As If She Is Proud Of Herself. She's 5ft7 And Weighs Between 8 And 9 Stone And She Goes To the Gym Two Or Three Times A Week For Around Two Hours. Is there Anything I Can Do To Help Her Because I'm Afraid She Might get Really Ill. Any Advice?