For home protection, nothing beats a Mossberg 500, mate! For personal protection, don't be fooled by what you perceived you saw that she can handle your .40 caliber. Don't ever, ever, ever choose a gun for her. Let her do the choosing. It may not be what you like, but if it fits her hands well, that is already a plus. Take it from me...it took me years to get to familiarized myself with an actual gun. Long story and I will not bore you with it. But I did went to a reputable gun store with a firing range and tested different models. Actually I did not find the gun that I want in that store but from another one, also with a firing range. Anyway, her first gun will not the only gun she will ever own. Let her do the choosing and save yourself from blame later on because you chose her gun for her.
Don't take my experience as a bible. Different strokes for different folks. Take into consideration your relationship with your wife, her attitude towards guns, etc...the best you can do is encourage her to choose a gun with the same caliber as your carry. It is a cheaper alternative.