How do I confront my friend? I'm really concerned?

you sound like a real friend, this girl is lucky to have you. If i were you, i would tell her how concerned i am. Tell her how much you care for her and that you'll be there anytime. Tell her how much she means to you. Don't "attack" her in any way, if you do she'll never open up. Get her to talk to you and just listen. Ask her why she seems so down, in a very subtle way. Whatever you do do not judge her in any way or form. I had a drug problem very similar to this, and my friends "thought" they knew more about it than me, and that really really pissed me off. You should tell her that whatever she needs you got her, whatever that is. Take her out to the movies or whatever, spend time w her and have a little fun, make her forget whats bothering her.

I'm not sure but I think this is anorexia nervosa, very common in teenage girls. Part of it can be to do with pressure (e.g. in the modeling industry) or from pressure at home or school to excel and do well (good grades...) and is also associated with a perfectionist personality. Physically, her bmi is 14.1 which would put her into the severely underweight category :( Anorexics tend to withdraw themselves from social activity- especially where eating is involved and try not to eat in front of anyone- they can be extremely secretive about food. She may not like you for this but tell her parents or teacher or someone you can trust- it may seem like betrayal but you could just save her life! Good luck, I know how it feels.

:)

confronting her a as a group won't help.

You should try and he the 'one' she can talk to often when people are in a bad place in their lives which it sounds like she may be emotionally then they don't want everybody to know whats going on in their mind. Let her know you are the one she can speak to, you won't tell anybody else, be patient with her she won't open up at first just let her know subtly you know something is wrong, ask her often what she is thinking, tell her you want to be there for her etc

When people start acting like she does they don't want people bothering them all the time asking how they are and lecturing them they just need one person they can fall back on in times of need.

so what i am saying is, lecturing her and confronting as a group will just make her distance herself from you even more she just needs one person to be there for her and it will help her to know somebody cares.