Dgludwig,
In the small size, also consider the LCR. I've heard the trigger is one of the best. It's now available in 3" .357. To be clear, I'm not recommending it, just that you consider it.
If I were to recommend something, it would be to size-up, and have her carry the revolver on her rather than locking it in the car.
A little bit larger revolver is not more difficult to carry and it's much easier to shoot well. If it were to be kept in the car, then there's really no reason for a small revolver at all.
My wife just turned seventy years of age; I mention that to give some relevancy to the adage, "You can't teach an old dog new tricks". Even though we have both had our "civilian" CCW permits for close to fifteen years and despite my on-going encouragement for her to at least keep a pistol in her purse on a regular basis, that's probably never going to happen. There is an easily accessible safe with a combination lock cabled to the infra-structure in each of our vehicles carrying a loaded revolver. Currently, there is a J-frame Smith, chambered in .38 Special, in her vehicle. For the reason(s) you cited, because she won't be carrying it "regularly", I think she'd be better off relying on a slightly bigger and somewhat heavier revolver that is easier to shoot well. But I want the gun small enough to tuck in her purse should the occasion ever rear its ugly head.
I
do carry regularly and after a thirty year le career and decades of competing with a handgun, I have accumulated lots of handguns that are suitable for edc and home protection but none that are exactly suited for the particular "mission" at hand. Two vintage revolvers that I count on for edc are a Colt Cobra and a Smith & Wesson Model 12; both being aluminum-framed guns, chambered in .38 Special, having a six-shot capacity (I insist on having six shots whenever practical which is why the next revolver I'm planning to get for myself is a Ruger LCR, chambered in .327 Federal Magnum). But these revolvers, including the LCR, are lighter and smaller than desirable for mostly "car carry" duties.
All of these guns I would recommend using with .38 Special unless you're handloading to the level she can control best. I wouldn't recommend factory 357 unless the gun has at least as much mass as a 686. But good .38 ammo can be very effective even from a short barrel, and it's safer to carry that than it is to have a hand-canon locked in the car. These aren't just my suggestions for a "woman," but from my personal experience.
Counting a Smith & Wesson Model 52 auto, I currently have seven handguns chambered in .38 Special, so it's not as though I don't like them. But when I'm shopping for a new revolver and I'm choosing between a .38 Special and a .357 Magnum; if both of them are the same or closely similar in size, weight and general configuration, there's no downside to the Magnum. I'll buy the .357 every time for its added versatility. With a Magnum, if I don't want the recoil and muzzle blast of the .357, I'll shoot .38 Specials in it. With a .38 Special, if I want more "power" than even Plus P stuff, well...
With all of this said, I'm still looking for the revolver having most of the criteria I listed in my original post for the reasons I've cited. I am leery of the safety failing in the case of newer S&W revolvers (I know that most people say it will never or almost never happen. Never is one thing;
almost never is another thing) I guess most important for my wife is getting the one with the best da trigger pull-most of the stuff I've read ranks the Kimber first, the Colt second and the Ruger a distant third.
labnoti, I really appreciate your well-reasoned advice. We're on the same wave-length and most of your suggestions are spot-on. I hope I've explained how the specific circumstances of my situation dictates slightly different approaches to the same problem. Again, thanks.