you should never ever pull on the shifter lever when driving, you just push it, that's why it was poped into reverse, she pulled on the lever, otherwise it would stop at neutral (Or press the button for the shifters down in the bush, just push them)
You're extremely lucky to not have broken anything. I've never heard of a safety switch for something like that, most cars can't lock up the brakes at 60mph anyway, so it wouldn't make a difference at speeds like that. Usually the weakest link breaks when you do that, (Axel, clutches... etc). We had a truck that came in that he slammed it into reverse while off-roading, snapped the 6" driveshaft in two.