Three blasts of brilliance slammed into Susan at once, she had her wand raised as though she could counter them and there was a white flash as the hexes struck the magical wood, but then Susan's legs convulsed and sent her flying into a corridor wall. Her head hit with a strange cracking sound, and then Susan fell down and lay motionless with her head at an odd-seeming angle, her wand still clutched in one outstretched hand.

There was a moment of frozen silence.

Parvati scrambled over to where Susan lay, pressed a thumb over the pulse point on Susan's wrist, and then - then slowly, tremblingly, Parvati rose to her feet, her eyes huge -

"Vitalis revelio," said Lee just as Parvati opened her mouth, and Susan's body was surrounded by a warm red glow. Now the seventh-year boy really was grinning. "Probably just a broken collarbone, I'd say. Nice try, though."

"Merlin, they are tricky," said Jugson.

"You had me going for a second there, dearies."

They wouldn't have been fooled for an instant if the burst was standard in Hogwarts. Though this could be something as simple as it not being well known, given the miniscule fatality rate in Hogwarts.

I don't think that's necessarily true.

If dying violently was enough on its own, then there would be scads of ghosts floating around, left behind by the war, even if you also discount those brave or unafraid-of-death enough to fight.

Moreover, Hermione's greatest fear (from the Dementor chapters) was dying alone, and Harry was there to assuage that fear. It's possible that that was enough to allow her to pass on, and that Harry's presence was the only reason that she didn't actually become a ghost. Which could have interesting effects on him if he ever found out.

Which doesn't mean that something extra isn't going on.