Try before you buy
I would find a CCW class, or gun range, where some folks would let her try various makes, models and calibers. A bonus would be letting her try various holsters as well.
I concur with Mr. H, in setting up a target at 5 rounds, and loading 5 rounds and shooting a piece of typing paper, folded in half, then in half again. At the sound of the buzzer, shoot as effectivley and fast as she can.
The paper will not lie.
We have a tendency when at ease, to scrunch and crunch around firearms, to allow us a better sight picture. When stressed we do not have time to do so, hence the importance of gun fit to shooter.
WE change with age, and not just eyes, and physical growth, as we do get aches, pains, injuries, arthritis, disease, surgery and so forth, do affect us, and how we do things, such as shooting.
This 5/5/5 is something we all should do from time to time, as I mentioned, we change with time.
i.e WE may have been able to shoot .357 loads from a revolver, but the paper may reveal we get more effective hits, with a .38 spl loading.
In my experience, the ladies do very very well with full size and Combat Commander sized 1911. Some do best with 200 gr, and 185 gr loads. Other guns include BHP, and S&W 3913.
Do not rule out revolvers. Smith K frames such as Model 10, 64 were favored by ladies, as were the Colt D frames ( Colt Detective Special). Other dedicated .38spls were favored, such as the Ruger SP 101.
Yes, we had ladies go with Model 19, 65, etc., in .357.
Re: 40 cal.
In my experience, none of the ladies liked this caliber, because of its recoil curve, no matter what make/model of gun used.
i.e. BHP in 9mm, was always, always favored over the BHP in .40 cal.
HTH