Highbass,
Rather than considering an inadequate .410 for turkey, why not address the problems your wife is having with her 20 gauge. What is the model she is using and what have you done about reducing the recoil? There are excellent after-market recoil pads available, some of them slip-ons so no gunsmithing required. The other thing is a mercury recoil reducer that fits inside the stock. What about an auto-loader also? Lets hear a little more information.
Jim