I don't think the O.P. has replied yet - so maybe he's still working it?
It's gonna be different for everyone, but my experience has been:
Size of gun proportional to size of woman (slim is sexy).
Trigger pull & felt-recoil will seal the deal.
I thought the J-frame airweight 38 was an optimal choice, but the trigger pull and uncomfortable grip shape + recoil = a new carry gun for me, not her.
The wife had a Colt 380 years ago, and won't let me forget that I'm the reason she 'used to' have it. Those little suckers have gotten mighty pricey since then, and the ammo ... as has been mentioned, has been a little scarce, lately.
A buddy recently turned me onto the 9mm Makarov (9x18mm). Right between the 9x19 & 9x17(aka .380) it seems like a decent compromise. Since it's a 'commie' round - the cheap ol' steel cased ammo is priced right & not too hard to find!
They may never make lasergrips for the Polish makarov I picked up for <$200 recently - but at that price, I can put one in each hand & teach her to shoot like yosemite sam!