I'm sorry, but I disagree on all points.
No. Even using bird shot with no choke (far from ideal for defensive work), at typical home defense distances, your spread is going to be around 4" or so. You
MUST aim to hit your target.
See:
Mad Gun Science: Is Birdshot Effective for Home Defense? | OutdoorHub
She can, and should, do that with anything, rifle, handgun, shotgun, whatever. And so should you. Don't go hunting someone. Unless you have to go get kids, bar your door, call the cops, yell out into the dark that you've called the cops, and hunker down. Stay safe. If you go hunting, there is a non-zero chance that you will be injured, killed, or even potentially end up on the wrong side of the law and spend the rest of your life in prison. No, I'm not joking.
With a shotgun?!? Nope. Unless you're running a 410, the Shotgun is going to recoil
more, be harder to come back for follow up shots, has less ammo capacity than an AR (or many handguns these days), and you still have to aim effectively (remember that 4" spread?).
Again, no. In all the actual tests I've seen, buckshot penetrates more walls than .223 from a carbine. The buckshot has more mass/inertia and will tend to keep going. The .223 destabilizes quickly after impact with drywall, tumbles, and eventually disintegrates. That said, in most cases, regardless of what you're shooting, it's going through a number of walls. It doesn't matter if it's buckshot, hollow points, or solid points. If it's from an actual gun, drywall ain't stopping it quickly.
Here's an example:
I agree that this is a tongue in cheek comment. Not only are you right that you should already have one racked, but the evidence seems to indicate that the sound of raking one into the chamber doesn't actually scare bad guys away.
In fact, more and more, even getting shot or seeing their buddies get shot (multiples are more common now) doesn't seem to discourage them. While it might, the growing evidence shows that, now anyway, there's a good chance you're going to have to deal with all of them once they commit to a Home Invasion.
Peace favor your sword,
Kirk