In general, I would never rely on it working. I have no idea how much power your wife's device draws, but I've had power outlets not be able to charge a late model laptop while I was using it (usually Airbus). I've had power outlets flat out not working (usually Boeing). Beyond that, you could get a last minute equipment swap to an airplane without any power at the seat.

If lack of power here is life threatening, relying on seat power should be Plan C or D.