I know women bobbed their hair after WW1 to modernize themselves, but how many cut it this short this early?

Looks like it was taken with a soft focus lens, like a Kodak 305mm or 405mm portrait lens, or a Verito/Veritar, or any number of other Heliar or PetVal derivatives. The soft focus usually came from deliberately uncorrected spherical abberations.

I found a passport photo of Mary C Barnwell over on Ancestry dated from 1919 (most likely for her departure for her honeymoon, as she was married that year as well).

The Barnwells are descended from the Beaufort Barnwells, a family with deep roots to the Port Royal area of South Carolina.

[Our Barnwell was, according to the photographer's captions, already a Mrs. in 1913. Mary Barnwell was an artist known professionally as Manya Konolyi. - Dave]

My usual practice with the enlarged Shorpy photo-of-the-moment is to leave it embiggened on my monitor as a temporary kind of wallpaper. But it just ain't happening with this one. Even my kids are complaining. The slight blur, combined with the steely oblique stare and the slicked-back hair, makes Mrs. Barnwell just too overwhelming. Positively glowing? Positively menacing!