I would let to get a shotgun for home defense. I would like to get something my wife could comfortably shoot. I am thinking about a 20 gauge Mossberg Cruiser
Good choice. I use a Mossberg 500 20ga cruiser for my house howitzer. My wife is pretty good with hip firing it at targets from 20 feet, and she's 5'5" and only weighs 120lbs.
9mm is bad news bears with small kids in the house.
20ga #6 shot seems to be more than enough to wage war on unsuspecting Hooligans. Or Flanigans!
I'm a girl and I love my Remington 1100 16ga. In fact I keep 3 shells in my armoire at all times just in case in the middle of the night I have to load quickly. It is an unlikly scenario but... I find that this gun is so easy to use and handle. I'm also not a large person at all and this gun doesn't overwhelm me in the least. I also find that I prefer using an autoload over a pump. Whatever gun you buy, I would at least let your wife shoulder it in the store and see how she feels about it first. Good Luck.
I definitely think the 20 is the way to go. Looking for one for my wife as we speak.
As far as actions, I'd go with an 1100/11-87 if she's fairly adept with guns and willing to train with it.
If not..well...I'm gonna be the jingoistic, nostalgic, old fart sounding stick in the mud here...(sheesh, and I'm only 32) and recommend a short barrelled hammerless double. short, manueverable, kiss simple operation, and I believe two shots is enough to get a homeowner through any invasion situation, especially if it's deployed as a barricade weapon rather than a wander all over the house weapon. When I was a kid my Stevens 311 got me through such a situation, thankfully with no shots fired. (on a prouder note I even refrained from peeing myself..barely! )