Whatever you two decide on, PLEASE choose a model with an exposed hammer. She'll be able to cock it easily, even on bad days, and the trigger pull in single action on the S&W handguns is SWEET!
I'd recommend an Airweight Model 37. It is plenty light, yet the three inch barrel does two wonderful things to a light revolver:
It improves the accuracy thanks to a longer sight radius, plus
The 3" barrel really tames the recoil vs. the typical 1 7/8" barreled snubby version.
That's what my wife shoots and she loves it . . . light, accurate and very comfortable to shoot!
The only photo of it that I've made is this one of several of my beloved 3" - 3 1/2" barreled revolvers. It is obviously, the smallest one . . . and is virtually as light as my own Model 37 Airweight that serves as my "always" (on me) self defense revolver!
Also, taking a firearms course from the Sheriff's instructor, she shot it so well that he exclaimed that she shot better than most of the deputies!
The grips are the original ones from this vintage 1971 specimen + a black Tyler T-grip. Together it is very comfortable to shoot!