The implication is it listens to you? Or she searched rotary phones after you spent an hour or two in the same places?

My gut reaction is that it listens to me, either directly or via some app, but I know Google has refuted this fact. I suppose this is testable too, so I tend to fall on the confirmation bias side of things.

The conversation didn't prompt you to look up any rotary-phone-related content?

I am confident it did not, that conversation was out of my mind as soon as it ended, which was why I was so surprised to see it dredged up again in my feed.

Your niece searched for rotary phones?

That's a good theory. I'm not on any social networks, however I do email her, so perhaps Google associates me to her via my contacts list?