For her, I'd suggest checking out the M1 Carbine as well. Especially if you can get good 100-110 grain JHP ammo. It's a light carbine (weighs less than an AR) and hits harder than a .357 Magnum at indoor ranges. Plus it's a self-loader so rapid fire is possible. It's good to at least 100 yards if it comes down to it. That's all she's likely to need. The best M1 Carbines are mil-surplus and you'll pay quite a bit for them. Most of the civilian made models aren't reliable in my experience (universal, auto-ordnance, etc).
For pistol caliber carbines, the caliber is least important. I've found that all of them will be softer shooting than their handgun counterparts, from 9mm to .45 ACP to .44 Magnum. Select a carbine that she feels comfortable with. For ammo compatibility reasons, if you want to use a .38/.357 cartridge, you'll be limited to a lever action rifle (Marlin 1894). Most are 18" barrels. Even a .38 Special +P will gain significant velocity out of a short rifle.
If nothing suits her, don't overlook the Ruger 10/22 compact (10-22CRR) with the 16" barrel. If you live in a free state that doesn't limit you to 10 round magazines, such a rifle with a 20-30 round magazine can be fired rapidly and will penetrate deep. Load with a 40gr Winchester solid or the 40 gr CCI Velociter plated HP.