Now, here's another option: what if you're just misconstruing what you actually saw? Say she tried to stab me, but never really made it all the way there - isn't it possible that your mind's eye just filled in those other parts?
...or, let me give you another example: what if the video's been tampered with? There was a slight delay between the video being sent and it being posted on the network. If Sentience is that capable of a machine, maybe it was able to mess around with what was being shown.
There are an almost infinite number of possibilities, but those are a few that immediately pop to mind.