I don't understand why this clueless widow doesn't go after government motor-vehicle authorities for allowing the pilot to drive a car. The principle is the same, and you're just as dead after hitting a tree in a car as you'd be after hitting the ground in an airplane.
The fact is that almost no automobile drivers are incapacitated by sudden cardiovascular incidents, even though they are not screened for cardiovascular health before being given a license. And conversely, there are still pilots who have sudden strokes and heart attacks, despite a more rigorous screening for pilot medicals. Which in turn implies that (1) medical incapacitation is extremely rare even in the general, unscreened population, and (2) screening people for heart disease won't necessarily reduce the already low incidence of incapacitation. The tests that might actually be able to verify if someone is at risk of incapacitation, at least in the case of cardiovascular disease, are extremely expensive and invasive, and thus not really practical. And the tests actually being used aren't really very reliable for isolating who will or will not be incapacitated.