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Well, first, make sure she can't handle a 9mm. A .40S&W has a LOT of snap to it; it's basically a REALLY hot 9mm. You shouldn't base her ability to handle any other round based on her experience with just one, especially the .40Smith.
Second, remember Newton's laws; the lighter the gun, the stronger it will kick because the same energy that sends the bullet out at many hundreds of feet per second is imparted the other way to the gun and the shooter. That means that a Kel-Tec is going to kick harder than a Beretta or CZ.
That brings us to the next point; what is this gun's primary purpose? Will it be a range toy for her to learn marksmanship, or will this be a carry weapon? If it will be carried, will she conceal or OC it? There are plenty of good guns with slimmer grips that have enough mass to make the recoil easily manageable. A pocket pistol is NOT a gun she will have fun with at the range. Conversely, if she's going to carry this weapon everyday, it's less about being comfortable firing 100 rounds than it is about being comfortable having it handy; a CZ does not conceal on the female frame very well.
I would make every effort to find her a 9mm she can shoot comfortably. 9mm is the cheapest defense round (.380 and .38Sp are in fact more expensive even though they're less powerful) and in a full-frame compact or full-size pistol it will be the softest recoil you'll find in a round that you'd trust her life to.
For the money, yes, the Bersa Thunder .380 is an excellent little pocket pistol. They make em in two flavors; single-stack and double-stack ("Plus"). If she can comfortably hold and/or conceal the double-stack, get that; she'll have an extra 4 or 5 rounds available. If not, the single-stack's still a 6+1, very easy topocket,and less expensive.
Ruger's LCP is a great "belly gun" (point and shoot at point-blank range), but like I said, small gun = large kick; she won't like it on the firing line.
The Walther PP series are excellent guns. The factor here will be cost; Walther's got a name and they sell it.
There is a U.S. maker named Kahr that makes striker-fired weapons similar in some ways to a Glock, but far slimmer. You might have her try one of those in 9mm or even .45 (.45 has more energy, but the impulse is longer so the recoil feels more like a push than a flip)
Now, if this is going to be solely a range toy, forgeteverything I just saidand get her a .22LR target pistol like a Buckmark, Beretta NEOSor Ruger MkII/III. Ammo's three or four cents a shot, and she'll have a blast with it at the range. I have a Buckmark whose main job so far has been to indoctrinate new shooters. It's a gun that shows you what you're doing wrong without making it unsafe to do things wrong. Hold a .22 incorrectly and you retain control; hold a 9mm incorrectly and it can fly out of your hands behind your head.