I think she's entirely correct. I consider "defensive driving" not to be about expecting horrible things, but rather thinking about (and taking action to mitigate) unsafe events.

I explicitly distrust other drivers, more than might be considered reasonable, specifically because there have been times that, had I not been so pessimistic, either I would have been injured or my vehicle damaged.

- I distrust turn signals. I've seen too many people approach an intersection that I want to turn into that had forgotten to turn their signal off. I believe it when I see your car change course, or start braking. (I also live in an area where many people don't bother to use them in the first place.) - I assume most people are speeding, and am conservative about pulling out in front of oncoming traffic -- which has saved my bacon when my car has stalled. - I assume people on the freeway going faster than me will cut in front if me. Strangely, this _reduces_ my stress while driving, as I am not surprised when it happens. - I approach my car from the front, so that I can see oncoming traffic before stepping into the road.

Being prepared for statistical outliers is important, because as a driver (or as a police officer) you have many encounters in the course of your career -- and your cumulative chance of encountering such an outlier increases the longer your career.