She is not the best example, in my opinion, because she is so muscular that the jaw muscle flexing out like that makes her face more masculine than elegant or majestic. Plus, its best not to show her body, just crop the face and emphasize the bone structure because it really goes against the case that square jawed women can also be feminine when you see chest muscles instead of full, well rounded breasts.
Anorexia helps to promote the over-prominent jawline. Notice the bottom of her jaw is sunken-in. And no, she isn't "muscular." Rather, because she doesn't have any bodyfat her muscle are shown through. In fact, she barely have any musules because you can also she her bone sticking out.