My daughter started shooting my Colt Gold Cup when she was 8, (she's 41 now).
You can get use to the recoil, nothing too it. One of the best hard ball (full load 45 ACP) was a young lady named Kim Dyer. She shot for the army and wasn't as big as a minute.
However: The 9 mm is also easy to shoot and ammo is cheaper. Cheaper yet for the 38 Spl revolver.
Yeah yeah yeah, lots of people say "get a 22" .............good idea but that wasn't what you asked about.
Of the two: 9mm vs 45, I'd pick the 9mm. If the revolver was thrown into the mix, I'd go that route.
Thing is, I cast and reload my own ammo for all three, and with todays prices I can shoot either cheaper then I can the 22.
Go fondle all there and buy the one that just jumps out at you.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071