I was considering a revolver but I do own a px4 storm 9mm that for some reason she loves to shoot so was kinda going with the semi auto "style" but will definitely keep it in mind. And as for Ruger I my self was very interested in the sr22.
Be careful about .22 revolvers. They tend to have a heavy DA trigger to reliably ignite the ammo. Some even have a heavy SA trigger. Might be a miserable experience for your wife or unusable. The SR22, 22/45, and Buckmark are better choices for most women. I have 22/45s and Buckmarks and my wife can plink with those all day long.