It wasn't a dangerous situation until the other car decided to drive into her. It's just not practical to ease off every time a car is overtaking you slowly - particularly as the OP has stated in average speed 50mph zones, where everyone is travelling within 1-2mph of each other. I'm all for defensive driving, but what you're suggesting is just ridiculous. Do you also slow to a crawl when passing junctions
just in case someone decides to pull out in front of you?
That's all well and good, except that someone overtaking you on a motorway isn't "obvious danger". It's a hazard to be aware of, but if you slowed down every time someone overtook you, you'd end up causing more of a hazard yourself by driving too slowly!
Then they can argue that in court and with the ombudsman, and see how that affects their bottom line
There's a difference between "keeping driving into danger", and "not getting out of the way quick enough". In your example, it would be a more accurate comparison to suggest that the "victim" would still be given liability even if they stopped, purely because they didn't slam it into reverse or swerve to go up the kerb to get out of the way of the oncoming car.
I don't disagree with any of those tips, but even driving defensively doesn't make you completely immune to stupid people doing stupid things