No, time travelling backwards will not stop her from leaving. The game will interpret the time travel as an advancement of days, so she'll be completely out of town if you go back. I'm sorry ): I hate it when that happens. You might be able to convince her to stay if you go to her house, though.
If she's in boxes, then there's nothing you can do to stop her anymore.
Sorry to hear that happened! That's really unfortunate that she never pinged you and that other villagers haven't told you about it.. Chances are low, but it can happen.
Oh no I'm so sorry to hear that! TTing backwards doesn't work unfortunately, I've tried that and I regretted it even more because my villager was gone and I didn't get to spend the last few moments with her.
It comes down to pretty bad luck. If you pass by other villagers who ping you first, there's a delay before others can ping you again. So chances are Victoria never 'got the chance' to ping this way.
But it also sucks that none of her other villagers have mentioned that Victoria was thinking of moving.. That also comes down to bad luck I guess.