When you ask random people to name a few square jawed women, sexy Salma Hayek is often part of the lot. She is very famous, feminine, but it's obvious that she has "the jaw".

However, she is not the typical square jawed woman. He chin is very developped, an A grade, projecting forward Jutting jawline is clearly defined, and front the frontal view, her jaw is square and wide.

But when viewed from profile, her jaw angle, is not particularly square. It's barely a B-.
It's a rare configuration, because usually, women looking square front frontale view, also have very square jaw angles.

See how the chin projects forward. These kind of chins are very resistant to the development of double chin, because the skin is kept tight by the above average bone growth.

Frontal view: you can notice that there is something about this jaw: it is wide. And square.

Here you can note what I mentioned: jaw angle is not particularly square.

On this image the imbalance is even more obvious: a lot of bone mass on the chin, not much and the gonial angles.

Special mention of Salma's teeth. Natural teeth, perfectly aligned and wide. Their squareness is due to the wear off. This kind of teeth, in the context of this solid jaw, usually have very strong enamel. From my observations at least. It is safe to bet that she has a good bite force and a lot of damage potential as she bites.