Better yet take her to a range that rents guns and let her shoot some different guns to get a feel for how they balance in her hand the and recoil of different calibers.

I love my 357 magnum colt, even better yet were the hot (flamethrowing) rounds my buddy Nick used to load for it before he got his nuts cut off by his (now) wife...

 

The best handgun for your wife is one that she won't use on you.

Go to a shooting range and rent some guns to see what she thinks she might like.

 

texaspower, you guys pick a gun or get a chance to go rent some, yet? two of my friend's wives have the S&W lady .38's, one of em absolutely loves it, the other one doesn't like it much and got a springfield 3" XD-40. I've run quite a few rounds through the 3, 4 and 5" XD-40 and a few glocks...I like the springfield waaaaay better, personally. of course I've never been disappointed with H&K but that may be a little excessively priced for what you're doing with it!

IMO, equally as important as the correct handgun selection is mental prep, a self defense or fight training class. training your mind how to react to a life-death situation so you know what you're going to do in 'fight-or-flight' mode is just as important for concealed carry as firing and reloading exercises at the range. check out Dave Grossman, I got to see a day long seminar by Lt Col Dave Grossman that he did for a group of swat and socom guys and have since gone through his book "On Combat", our minds/bodies do crazy things when someone intentionally harms you!

 

I've got a Ruger SP101 with the snubby barrel, my wife loves the thing,keeps it on her in the woods.
She never liked any of the autos I tried to get her to shoot.
I've got a Para-Ordanance P-14 45acp that I love,she can't really operate the slide though.