After thinking about this a bit: most full-size service-pistols will have recoil springs in the 12-16 pound range, with a few maxing out a 20 or so. Assuming a hammer or striker spring of normal strength, that's going to add another couple of pounds to the pull, if it's not possible simply to cock the hammer and remove that from the equation.
Either way, you're talking about needing to generate a differential in force between the left and right hands of about or below 20 pounds, which means 10 pounds per hand. If you can lift a ten-pound weight with each hand, you have enough pure strength to rack anything but very heavily-sprung compacts or 10mm's or the like.
So what's the problem? Grip/purchase. Since the hand on the grip of the gun has plenty of purchase, and since the frame will be pushing back into one's palm, that's not going to be the issue.
Ability to grab the slide and not lose grip has to be the source of the problem for all but those who are so enfebled as to have difficulty lifting the gun itself. The obvious first step is to have the shooter try every different (safe) way to grab the slide. Some people may get more grip with the overhand method. Many will get more with a pinch between the thumb and side of the index finger (the human hand was specially designed to apply force between the thumb and the fingers, not finger tips to palm). Maybe there's a fixed rear sight with a shelf to get more purchase.
If the slide still slips through the fingers, one could look for something with stronger serations. But that may be counterproductive. Many people's grip on things fail not because of a lack of strength, but because the friction or pressure on their skin becomes uncomfortable. Skateboard tape on the sides of the slide may be less painful than serrations.
If that still fails, you can add a slide racker. Slide rackers are common on race guns. They'd be unorthodox on a home defense pistol, but I can't see any problem other than that the pistol may not fit in a shallow drawer or in the original box or in some small safes.
In any event, if your wife has enough hand strength to pull a DA revolver trigger, and enough arm strength to lift, aim, and fire a gun, the requisite strength ought to be there. At least that's how it seems to me.