>>1
The best thing you can do is, talk to her, tell her that you're worried about her weight, tell her you are not comfortable with her being so thin, tell her that you care about her and it worries you, and that you think she should eat a little more unless it becomes a health risk.
If she turns around and says, LOL FUCK YOU I LIKE BEING A SKELETON I WANT TO LOOK LIKE UGLY GIRLS IN MAGAZINES.
Drop that bitch like a handful of dog shit, since she isn't worth keeping around anyway, let her self indulge in anorexia, tanning, and large amounts of makeup, and lol to yourself because she's an insecure freakshow.