So, basically, nothing counts as Azeroth's death?
It's logical that she would be the harbinger of the Old Gods.As for the Windrunners, I think Alleria is a red herring. She isn't really logically tied to Azeroth's fate as far as we know.
Sylvanas died at the hands of Arthas, by throwing herself off of Icecrown and shot to death by Lord Vincent Godfrey.Sylvanas, though, has died two times as the Banshee Queen (three if you count her death at Arthas' hand, but I think of that event more as her birth). If she died again it could be seen as her third.
That's BfA.
Where?