For ammo we were looking at the 175 winchester silver tips. We're not opposed to smaller calibers, this is for a female business owner for carry-on personal defense handgun purposes.
I myself have used the .40 glock and think it was an easy to shoot hand gun. Maybe a .357 sig or .40 would be the way to go? I think a little more stopping power than a 9mm would be preferred since the sole purpose of this gun is to stop an attacker. This is where the 10mm caught my eye, similar to a .40 cal, with a little extra. The female is 5'8 175 pounds so I would think with training and practice using this firearm would be feasible.