It's already been said, but it surely sounds like "limp-wristing". The inertia of the slide needs something fairly solid to react against to cycle and feed properly. It's pretty elementary with all handguns, but hand, wrist and forearm should be locked together in a straight line. No need for a "death grip", but a pretty solid hold is required. I don't know what kind of arm extension you are employing... fully extended as in bullseye shooting, maybe? Try, perhaps, the two-hand "push-pull" technique, with your arms drawn in slightly. Everything should be nice and tight but not to the point of rigor mortis. It should also reduce the problem with any recoil sensitivity that you and your wife may have.

Good shooting.