If you are shooting ammo of unknown grains... then that may well be your issue... your ammo.
But 12" groups... I'm guessing at 100 yards... heck ammo can't fix that.
Either something in the gun has come loose, your scope is broken, your not as good a shot as you think you are (take that with salt its a joke

), or you just need to sell that joker.
I think you have a right of redress with H&R if thats all she's got. I'd try some different ammo, recheck everything again, maybe bring the gun to a gunsmith and have him check everything out.. and shoot her one more time.