I wasn't overly annoyed with her... up until she started attacking the TV like it was going to make the broadcasters hear her or that it was the TV's fault the broadcast stopped airing...
As for what happened, my thoughts so far have gone: Alien attack, Atomic bomb, Mount Fuji erupting, a comet/meteor hitting the Earth.
As it stands now, after the broadcast indicating it was worldwide, my thoughts are leaning more towards either a world-wide alien attack, tectonic shifts causing all/most volcanos around the world to erupt, or a comet hitting the Earth.