Maybe the metrosexual men need a 9 MM mouse gun but hillbillies aren't recoil sensitive.
However manly you niece is, small people have small hands. I suppose I could man up and shoot a 17” pull, 10 lb., .50 BMG; but that doesn’t make it fit me, or the recoil less punishing.
I’m a 5’10” male, and there are pistols that are too large for my hand. Sure I can make them go bang, but they are still less than ideal. The 1911A1 is the right fit, but I suspect the releases would be easier if I were 6’2”. At 5’1”, it is effectively a 2 handed gun.