Hmmm? If the primary issue is some low life breaking into your house, a shotgun is the only way to go and as stated above, use 00 Buck. I just bought a Remington 870, with the 2 shot extension and an "18 barrel this week to add to the collection. If you are looking for a handgun, I really like Glocks.
http://www.glock.com/english/index_pistols.htm I have a Glock 20, 10mm and love it, but that would likely be a little to much power for your wife, if she hasn't been around handguns. If it is more for protection, consider a Lasermax for the gun. Whatever you point the dot on, is where your bullet is going to go.
http://www.lasermax.com/
Ammo is also something you will want to consider. I have 4 high capacity, 15 round clips for my glock 20, all loaded with different bullet types and love the Corbon rounds.
http://www.dakotaammo.net/
They make very hot rounds and are great for various self defense issues. The rounds are expensive (Not plinking rounds) compared to a Federal round, Remmington rounds, or something of that nature, but are what you want in there in a life or death situation. When I am in the back woods full of grizzly's, that's the only round I will have in the gun. The same goes for street, or home defense.
I hope that helps a little, I didn't get to deep into it and tried to keep it basic. Good luck.