During 15 years as a police firearms instructor, I found many
officers very sensitive to recoil, had a large problem with pump shotguns.
Officers that simply couldn't qualify with the 870 pump, would qualify the very first time with the 1100P gas operated semi-auto.
After trading my wife's 20 ga 870 for an 1100 police in 12 ga., she was able to go from light trap loads to heavy buckshot loads without pain.
870 trap and skeet guns are HEAVY
! That helps with the recoil. But 870 defense/police shotguns are feather light
, and the recoil is brutal. Even in 20 ga.
Get your GF an 1100 police in 20ga, and she'll be able to shoot the heaviest buckshot loads without pain.