On a direct curved trajectory, she got the inherent force of the bullet (diminished by air viscosity forces) but added by a vertical drop component regained after dropping from the top of it. A “drop only” energy or force of work into her head would be much smaller, but from a 50 slug still significant. A hail storm of that size is painful, let alone of that mass or density. I dunno, if people can hit and kill animals with long barreled muzzle loaders at these distances, it still is possible, I guess, to kill someone that way by accident, imo. Heavy bullets have inherent higher inertia and thus are less prone to energy dissipation than lighter bullet. It has to do with Reynolds’ number of a ball of lead. Check the ration of Inertia to air viscosity...
http://www.grc.nasa.gov/WWW/BGH/reynolds.html
The higher the density and linear density of the bullet the more energy it keeps. An arrow is light but has great length and thus comparatively large linear density and could be deadly when merely dropped, and so may be a large calliber bullet compared to a pellet size one. And also the following
http://slinging.org/wiki/index.php?title=Reynolds_Number&redirect=no
“” Reynolds Number From Slinging.org Wiki The Reynolds number is one of the main variables used in sling ballistics calculations. As a general rule, if two bullets have the same shape and Reynolds number, they will show the same aerodynamic behavior, even if they have different sizes or move with different velocities. Therefore, ballistic tables and formulas are greatly simplified when put in terms of the Reynolds number. Another advantage of the Reynolds number is that it is dimensionless, that is, its value is independent of the unit system used to measure it.