When I took the MSF course and started riding 6 years ago, I quickly started to be very uncomfortable at any blind intersection, where I cannot see if someone is not slowing down for their stop sign or red light.
At first it made me un-easy, it did not take long before it made me start to slow down so I can look both ways and have an escape path or enough time to stop.
When I drive our car my wife frequently says things like "why are you slowing down?! You have the right of way! That person HAS TO stop!...." when Im driving defensively.
She stopped complaining as often when I was passing a car on the interstate in NC at 75mph, and just as I got in the blind spot of the other car, it started coming over in our lane. I had the cruise control on and nailed the brake. The antilock brakes and stability control system on my 2014 Fusion kept the car straight and she missed us.
I few weeks ago my wife had a close call of her own. A car stopped in the center left turn lane with its left blinker on, decided to pull back into her lane just as my wife was coming up on it.
Defensive driving is all about being aware of what could go wrong, which car might not stop, which car has its turn signal on but its not going to turn, who or what might be on the other side of a big vehicle that I cannot see, and who cannot see me.... and when you see the potential for trouble slowing down and backing off.
As in your wife's case a minor bash up in a car is normally not serious for the occupants, but on our motorcycles its life and death.
There is a whole thread about near misses, I dont think anyone has yet posted to it that actually got hit: