Why not just get a Mossberg .410 and train her on the controls?
Because a long gun is unwieldy in close in door environments. They take two hands to operate. Seldom are you going to find both hands free.
In home defense chances are you're going to have something in the other hand, flash light, cell phone while on the line with the police,.....something.
I learned that in LE, we did tons of building searches, sometimes in pairs but most often alone. I can't remember the time I had both hands free.
In self defense classes I give my lady students an option. They get to try a variety of firearms. Including shotguns, rifles of all sorts, pistols big and small and the Judge.
Shotgun shells in the judge aren't that bad, I haven't found many women who have difficulties with them but most find them too big.
My wife got a for horse back riding in snake country. Works perfect for that but she carries a S&W 637 for SD.
You say your wife has a snub nose, and you have a Judge. Let the wife shoot both and let her decide.
Women are much happier with something that works for them then they are something we tell them will work.
If your wife isn't comfortable around guns then she needs shoot them more.
First thing I tell my students is that I want the gun as comfortable in their hands as a cell phone is in the hands of a teenage daughter.
I get a lot of ladies who never handed a revolver or pistol before. I start them out with a couple hours of nothing but 3-3-3 drills, meaning they draw and shoot three rounds in three seconds at three yards. I do this before I start on defense scenarios. Most are much more comfortable after the first night, seldom does it take them more then two nights.
Don't have classes lasting over two or three hours. Its better to have several short classes then one long extended class.
But for heaven sake, let the lady choose her gun, what I like and what my wife likes is as different as night and day. Your job is to make sure she gets over the "uncomfortable" feeling. Get her training if possible, it not get her to the range to practice. And make sure she keeps it up,
Rule of Thumb: A small gun one can shoot beats the heck out of a big gun they can't.