(contains spoilers for final episode)
Maybe I'm missing something about the whole time travel thing but something has been bugging me:
So, Christy and Dumain travel back in time and appear before the Triad and Dumain, so there's two Dumains at once. Then the Charmed Ones and Billie appear from the future, and the Charmed Ones destroy the Triad before Piper destroys Dumain and Past Dumain, then Billie has to kill Christy.
But, only the present Christy was killed, what about the past Christy that would be somewhere else? Piper had to kill both Dumains, does that mean Christy of the past is still alive? Or would she disappear when time caught up with itself?