> how could she have predicted the outcome?

I don't think it's hard to predict that police will harass a black person in a white neighborhood if someone complains, and my guess is that it's not the first time it's happened in that particular neighborhood.

> In what sane world do the police seek out unfounded accusations on social media then act on them?

I would guess it's not the first time the police pulled a report from Nextdoor.

> In what sane world

I don't know, but if that's your premise, this particular world must be very confusing for you ... :)