I would say forget the .410 (although I learned to hunt with one). I would suggest you look at pair of Remington 1100 20 gauges. Not a lot of recoil, not over kill for squirrel or rabbits and you can also use it for bird shooting if you want to take that up. A good .22 would be fine but it will limited you when you want to branch out to other types of hunting.
The 20 gauge in an 1100 will not have the recoil of a 12 and depending on your wife's stature, you might want to look at the LT-20 Youth model for her.
http://www.remington.com/firearms/youth/1100ythsyn.htm
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'To sum up, one does not hunt in order to kill; on the contrary, one kills in order to have hunted.' 'The Ethics of Hunting' from 'Meditations on Hunting' by José Ortega y Gasset