ORIGINAL: bronko22000
Any of the above referenced handguns will suffice. But you should BOTH go to the gun shop and decide together. You don't want something too big for her hand and/or too small for yous.
But for strictly home defense, I would have to agree with stalkingbear's suggestion of a short barreled 20 gauge pump shotgun. Loaded with #4 or #6 and an open choke it will definately stop a home invader in his tracks. And it would be much easier to hit him with at night. And even if she ran out of shells, it would still make a handy club to beat the crap out of him.
Shotguns are the ideal home defense/protection weapon. Any of the pistols mentioned have the drawback of possibly penetrating an interior wall and killing an unintended target. This is not the case with a shotgun. You don't have to worry about accuracy in a stressful situation. Finally, the pumpshotgun has one more advantage over a pistol, the sound of chambering a shell. Nothing else sounds like that. If I had broken into a house and heard that sound from down the hall, I would be getting out fast.