While the caliber of the firearm is relevant, and in some cases it is even decisive, the main point is that this was combat.
In combat you have the weapon, but far more important is the caliber of the person who is engaged in combat. Combat, once begun, is usually to the death (or something approximating death).
She was fearless, and was obviously willing to fight to the death.
Her caliber as a warrior was what made the difference. The handgun caliber was secondary. She broke the evil one’s will and kept going as long as it took. Totally heroic.