I'm an instructor and I've worked with women with hand strength issues related to arthritis and similiar conditions before. Some worse then others, but I'm talking about actual medical conditions here, not just people who never developed much hand strength in general.
Almost every one of them told me in advance that their hands weren't strong enough to let them use an automatic. They had tried them in the past and couldn't work the action,etc. I've probably had eight or nine women with arthritis or other joint issues tell me this exact same thing.
Guess what? So far, I'm at about 90% in being able to teach them how to properly work the slide on a semi-auto pistol and show them that, yes, even with their health issues, they don't have to just use a revolver.
(And the eight or nine are JUST the women with actual medical problems such as arthritis or other joint issues. I've taught many, many, other women who just didn't have much hand strength in general, but not related to any significant health issues).
The only women, so far, that couldn't use centerfire automatic was one with a very advanced case of arthritis. She was in her late 50's and her condition had worsened severely over the years. The really bad news is that she *already had* a revolver: She had a J frame that she had for years that she used to be able to shoot without problem. Unfortunately, she no longer had the strength to pull the trigger more then two or three times in a row. By the fourth shot she had both index fingers in the guard and it took all her effort to discharge the gun and her accuracy was totally gone.
For her, we finally found the only pistol she could operate and shoot well was a Ruger Mk II .22. Not the best choice, by any means, but the only one we could find that worked.
For everyone else though, I've seen the light bulb go on over their head as they realize that, yes, they don't *have* to just shoot a revolver and, if they want, they can shoot an automatic. Some centerfire autos are easier to rack then others. Spring resistence and the size and shape of the slide play a role and some women couldn't rack certain pistols, but could operarate other centerfire pistols.
But, the big issue is *technique*. With the proper technique racking the slide on an auto is more about leverage and power from the hips then about pure hand strength. Pax has a write up on the technique on her Cornered Cat website, but it is MUCH easier to explain and demonstrate and teach in person then for someone to learn from reading the description.
I'm not trying to brag: As an instructor I'm nothing special.
My advice is to find a good, experienced instructor in your area willing to work with her one-on-one. You want someone whose dealt with this kind of issue before and who has a nice variety of handguns for her to try. He needs to know what techniques work best for women in general and specifically have an idea on how to work with someone with arthritis or other health issues. Instructors like this are out there.
Now, I'll admit, that I could be wrong and your wife's joint disease is as bad as that one student I had, and that no matter what technique she uses, she just can't work the slide on an auto. BUT, before you decide that, have her work with a good instructor first. You might be surprised and, if nothing else, he shoudl have some revolvers for her to try as well.
And, to answer the question you *asked* instead of just telling you what *I think* you should hear, my revolver advice is to avoid the J frame pistols and try the K Frame guns. The smaller J Frame guns are harder to shoot not only for their small grip size but also because the trigger geometry is different. The leverage points are different and generally the guns have a heavier trigger pull that can not be lightended very much.
The K frame S&W's though have better leverage points and the pulls can be lightened significantly by a good gunsmith. This, combined with the bigger grips, make them easier to shoot. The K Frames are available (used at least) with 2" or 3" barrels. I use a 3" Model 65 as my carry gun.
If she does want a J Frame, the double-action only J Frames can be worked on to have better DA trigger pulls then the other J frames. That's because they lack the single-action notch and the gunsmith can smooth them up and slick them up more. If she does get a J frame I recommend a DAO only Smith with a good trigger job by a qualified gunsmith. Buy a used gun for this, btw.
But, seriously, have her work with a good local instructor. You both are likely to be surprised. And, if she really can't work an auto, he can help her get the most of out a revolver.