Webleymkv gave you an excellent reply. The only thing I would add is that recoil with .38spl loads in the 2.25" SP101 is still very mild. More than the big Smith, sure, but still very tolerable. My girlfriend could shoot +P in my SP101 with no problem, but wouldn't touch a J-frame.
I think the SP101 is an excellent choice for your girlfriend's purse gun. Don't get the Rossi.