Honestly, she wasn't putting that much thought into it. She was just parroting a myth that's been around for a long time, and then trying to defend it when challenged by something that didn't make sense to her by bringing up something else she doesn't understand just kind of assuming the answer is in there.

If I was actually going back and redoing the conversation, I would have asked her how many revolutions per minute it takes to keep an object in the air when tied to the tip of a rope (demonstrating if necessary) and then follow up by asking how many revolutions per minute the earth has. The myth she's spouting is enabled by people not understanding that all that speed they are citing at the equator is only part of the equation, and that they have to divide that number by the size of the earth. Reframing the question in terms of revolutions per minute makes it a lot more intuitive, since a single rpm is obviously very, very slow if you want to keep something aloft, and anyone who knows how clocks work can instantly figure out just how much slower the earth's spin is.