man gonna whiplash me when theres gonnna be a time travel shenanigan
If it were, my hypothesis is that, She did in fact killed them, but rather, her future self. But instead of two person in a single timeline, its more like she's swapping with her past self with her future self. which would check out as I think it has to do with the fact that almost every testimony of her, refers to her in different weight and look multiple times within the span of a month.
That's Theory 1.
Theory 2, I'm guessing is that his Shinju's dad may have met with her mom at some point, or her.