First of all, I do agree that 50 grains powder and a 223 grain PB is not an ideal load. But I do think it will cleanly kill a deer at 50 yards. I remember reading stories of hunters back in the 1700 and 1800's. From many accounts I read, a "normal" deer load was about 50 grains of powder with a PRB (about 177 grain bullet). Many guys also used to hunt deer with a .45 cal PRB, which most of us would consider too small for deer.
Another thing that hasn't been mentioned- what size of deer are we talking about here? There's a HUGE difference between a 275 pound Canadian buck, and a 85 pound Florida doe. I would not use 50 grains of powder with the 275 pounder, but would consider it adequate for a small-to-medium sized deer.
If you are able to up the powder charge or use a different bullet, I think it would be best to do that. But if that is not possible, I would take your wife out hunting, just be very picky about the shot selection.