I'd say that if you are the more experienced and versatile shooter vs. your wife, then get what SHE is most comfortable with, and you will adapt easily. (If she were the more experienced shooter, I'd say get what you prefer, and she would adapt.) If she likes 1911's and 357's, you need not 'step down' to a 9mm, even though I think the consensus is that a 9mm WILL do the job.
One thing to consider is that if you fire a 357 or most 9mm's indoors without hearing protection, especially several times, you may wind up with permanent damage, vs. firing a 45 ACP. If you have a "first time, every time" 1911, personally I'd go with that. If not, a revolver, though I'd prefer a 750-fps'ish larger caliber bullet vs. the ear-punishing 357 Mag.
Like others have said, don't discount a shotgun or carbine of some sort, and of course a carbine could be ammo-compatible with your handgun of choice, most likely, whether 9mm, 40 S&W, 45 ACP, 357 Mag, 44-40, 44 Spl, 44 Mag, or 45 Colt. The main problem is with a carbine, you may not tend to have it in-hand when answering the door*, and a door-kicker could catch you or your wife defenseless, vs. if you have a handgun in your bathrobe pocket or whatever.
Ideally each of you should have your favorite handgun, maybe compatible with the same ammo or even same magazines. If you still can afford to have a couple long guns so much the better. Even if riots take the neighborhood, and all you have is two handguns, the two of you spittin' out 230-grain hollowpoints from a 5-gallon bucketful of ammo would be enough deterrence that you really wouldn't need much else.
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*
now out "in the country" it isn't at all unusual for folks to tote a long-gun if they answer an unexpected knock at the door...sometimes around these parts, a travellin' salesman just might think he'd stepped onto the set of 'Secondhand Lions'**...
** if you
haven't seen
'Secondhand Lions', you really need to click on the above link. You will want to buy or rent it immediately after seeing the salesman scene.
![Laughing :lol:](./images/smilies/icon_lol.gif)