You might look at a Kahr K9 or CW9 9mm semiautomatic. They are small (too small for my large hands anyway) and yet can handle 9mm Luger ammunition.
Concerning not wanting to hurt your hands, a too-light gun will increase the felt recoil from a given type of ammunition. My wife has rather severe arthritis in both hands, and as a result has to shoot a revolver heavy enough to dampen out the recoil to a manageable level.
Well. Complications. So light weight makes for more recoil...? What does your wife like?
She should try a semi-auto. In a semi, part of the recoil energy goes into operating the slide, resulting is less recoil energy going to the hand. (This presumes she's able to hold it firmly enough to ensure reliable cycling)