Smith J frame with an enclosed hammer. 442, 642, 640, etc... Only two “controls” - a release for the cylinder to load/unload, and a trigger to make it go bang. No worries with cocking a hammer (or a novice trying to lower a hammer...). As simple as it gets.
I got my mom a 642 and put a hogue tamer grip on it. The factory trigger is a little heavy, but a Wilson Combat spring kit will cure that. I’ve put one in all my J frames.
A DAO model K frame will serve the same purpose, but you won't be sacrificing a round and the gun will be much easier to shoot proficiently...especially with +P loads. IMO, a J frame should be fairly far down the list as a home defense weapon for someone with little experience or training.