How often do you see female characters in film and television killed as a way to lead a male character to have a revelation or an epiphany? Pay attention: it's an increasing and disturbingly common trope. Ultimately, it's sloppy, lazy writing. Women are so often underrepresented in film and television anyway, and it's just so disappointing when they're included just so that they can become dead bodies for men to grieve over. I just can't believe that the writers couldn't come up with a more original, less cliched way for Churchill's character come to grips with the gravity of the disastrous fog.
Anyway, Venetia's Magical Corpse conveniently saves Churchill's political career, too. He's captured by photographers at the hospital, and the newspapers trumpet that he's one of the only political figures to truly care about the problems caused by the fog. And then, the fog lifts.