its NOT just the stock, its hopw the stock fet this person, if they have small hands, odds are they need a stock with a grip closer to the trigger, , so they can have a better hold on the gun, just swapping stocks(as many just copy the OEM for grip location and size) isn't going to change the distance on the grip to trigger,

I would suggest to measure from grip to first stock bolt hole and current stock and any possible replacement one's
so you can get a better idea if "X" brand stock is any better or not before spending any money
a thumb hole stock, will most likely also have the same distances or Worse, as many have like a palm swell, and if this OP has a small hand, that can make matters worse for them, as there part of the hand getting hit at recoil will still be there to get hit
MIGHT allow some more meat to hols, but again if small hands now are getting hit, its most likely due to they cannot hold onto the current stock properly and the hand is coming off and getting HIT
so a larger thumb hole or palm swelled stock small hands cannot hold tight enough I guess and come off at recoil

sort of a form issue due to size of shooter here I think