I am always stunned by questions like this. Of course the .410 shotgun is an effective self defense weapon in and around a home. That lead is coming out of the barrel with about the same power as a .44 magnum. Using a 3 inch shell, with no. 4 buck, is devastating. Even no. 4 birdshot, at 20 feet or so, is devastating.
The .410 single shot is a favored self defense weapon among older women in Memphis, and has been for years. Recently, a woman shot an intruder at about 15 feet, coming down the hallway towards her, using heavy birdshot. Almost the whole load blew clean through him, and he was dead before he hit the floor. The key, I believe, is to go with a full choke, not a cylinder choke as with a 12 gauge.
The most important thing is for your wife to be comfortable and competent with the weapon. If she is happy and comfortable with the .410, then this is definitely the weapon for her.
Regards, Mannyrock