I wouldn't exactly describe of her appearance as anorexic; she just has a very lean, lithe, and toned physique. If she really was stick thin, I would be seeing bones poking out, which I do not see in this photo (or any of the other screenshots of her), so she is not anorexic. Tifa, Yuna, Rikku, Vanille, and Lebreau all have similar physiques.