This sadly reminds me there are actual people out there that starve themselves to fit a characters profile. Get a freaking hamburger for crying out loud.
People are looking too far into the new girls figure. This mangaka just has a way of drawing skinny girls like this. It doesn't have anything to do with an eating disorder
Like many people already pointed out, the first thing I automatically thought of when I saw the coloured illustration was "anorexia?", either way, it doesn't look healthy.