There are a lot of good comments above. I'll add some of my experience as an instructor.

Knoxx stocks are great in a lot of ways but a really good cheek weld can cause an abrasion. I've seen it a few times with smaller officers.

A lever gun in 357 or 44 is probably a very good solution. Even in a '92 style gun, the recoil isn't bad at all. They're pretty simple to use, also. If you're set on a shotgun and your wife is willing to put some work in, I'd strongly suggest the Beretta 1301. It's the softest shooting SG on the market, but familiarization will take some practice.

Also, when it comes to long gun recoil management:

https://www.youtube.com/watch?v=3eVHl-fBB-0

I've had a lot of success with this technique. One of our female officers who weighs just a bit over three digits started using the technique and doesn't fear yearly quals nearly as much anymore.