Riders of the Silences by Max Brand — Read

She wore a cartridge-belt slung jauntily across her hips and from it hung a holster of stiff new leather with the top flap open to show the butt of a man-sized forty-five caliber six-shooter -- her first gun. Not a man of the gang but had loaned her his guns time and again, but they had never dreamed of giving her a weapon of her own.

So they stared at her agape, where she stood with her head back, one hand resting on her hip, one hovering about the butt of the gun, as if she challenged them to question her right to be called "man."