Best advice is to take her to a gun range where you can rent a selection of different .38 and .357 revolvers. Let her try each one of a type...
- J-Frame 5-shot steel
- J-Frame 5-shot alloy (lightweight)
- K-Frame .38 2-inch (Model 10, 64)
- K-Frame .38 4-inch (Model 10, 64)
- L-Frame .357 4-inch (586/686)
- N-Frame .357 4-inch (627)
Besides being able to shoot it, the gun should fit her hand well enough that she's not stretching to reach the trigger or hammer. It should not feel so heavy to her that she can't hold it outstretched for six slow shots. The recoil should be tolerable for her.
The older .38 Special revolvers can be found at bargain prices sometimes.
S&W Model 67 (circa 1979) .38 Special
The above is one of our HD guns and it's accurate enough to put all six rounds into a 1.5" circle at 25 yards.