There were multiple studies done on the ideal type of beauty. Often times, Natalie Portman came up as the prototype of the most beautiful female. An example of such study can be read here. Indeed Natalie Portman is a universal symbol of femininity and beauty, and she plainly deserves this title.

From my observations she is more of the strong-jawed type than the contrary. Yet most of these studies rate a soft jawline as qualification criteria for women.

So what's the deal? B grade type of jaw angle (above average squareness, but nothing excessive) is in fact the de facto standard of beauty even for women, even though it is hardly recognized by society. People just can't dissociate square jaweness from masculinity.

The theory brought forward in this site is that square jaw pattern is an efficiency trait, and efficiency is a stimuli of beauty.

As of excess squareness (grade A jaw angle type) attraction.... this is more of a personal sensitivity than universal beauty criteria.
There are two considerations at stake here: universal beauty criteria, and personal attraction sensitivity. Some men are attracted by super squared grade A women, although this type of jaw angle pattern, is not a universal beauty criteria as I believe, type B is.

This is NOT a woman with a soft jaw line. Jaw angle is noticeable, jawline is long, and chin thick, well developed. B grade jaw angle, B + chin.
Also notice the feminine forehead, with absolutely no brow ridge bump.

This profile is perfection, but NOT a slender face build. Look at the length of the jawline. I love the lips, and how the chin advancement positions the lower lip in perfect vertical alignment with upper lip and chin point (grade B chin). This looks like an antique greek statue profile.

Very beautiful woman. Feminine. But look at the jaw box: cheekbones are wide and heavy. Jaw is wide. That is not a gracile type face.

Do you see what I mean? This is a robust face structure, well architected on wide cheekbones, and proportionally wide accompanying jawline.

Young Natalie, you can already notice the strong face structure: jawline is so well defined because the jaw is wide. Health = beauty, and a healthy face develops into robust face structure.