I recommend it in 357 magnum loaded with +P's.
Have her pracice with 38 wadcutters and slip a magnum in for thrills! (only if you have no concern over which whay she will shoot the next round!)
Seemed the .38 was just a little lighter. Besides, at 10 yards I would rather she shoot more accurately which I think is usually the case with the relative muzzel blast from a 21/2 inch barrel.
LOL! Now that's just MEAN!
I have a good friend who taught his wife to shoot a .22 rifle and had a 12-gauge shotgun for home defense that he told her didn't recoil any more than the .22. He figured if she ever needed to use it, it wouldn't matter.
Then one day she when he wasn't around she took the 12-gauge to the range with her.
He slept on the couch for a month...