Given the experience of the mercedes driver I find it unlikely that he has done something which he doesn't do just about everyday when he is driving on the autobahn.
If we assume that, it would seem to me that the woman must have panicked or simply been surprised by the fast approaching car and thereby lost control of her car while changing lanes.
Just because it was a woman and her child that doesn't mean it was the mercedes drivers fault.
I am sure we wouldn't have this discussion if it would have been a mercedes test driver who panicked and lost control over his vehicle.
I regularly drive on the autobahn and pass other cars at very high speeds which by the way is very normal on the autobahn,and if someone panics because I overtake them, that simply isn't my problem, that is their inexperience of driving on the autobahn.
When I approach a car from behind at the autobahn at high speeds I usually first wait and see if they have noticed me, if not I slow down a bit and flash my lights once or twice from a distance, if they don't change lane I slow down and stay behind them at a safe distance so that I know that if they brake I still have time to brake as well.
In other words I drive in a way that i feel is safe for me whatever the driver in front of me would suddenly do.
I can't imagine a test driver driving any other way than putting his own safety first,which I am sure we all do!!!
By approaching so fast that your own safety would be at risk is plain stupid and inexperienced which i don't think the mercedes driver is.