> This is literally what she did though! Why else would you not just erase but rewrite with random data?

I do essentially this on a regular basis. It's SOP when I'm done with a piece of electronics. It has nothing whatsoever to do with the FBI -- it's because I don't want anyone who finds (or buys post-consumer) the device to find my data on it.

I'm currently procrastinating on recycling a couple of old busted Android devices specifically because it's a real PITA to scrub them with any degree of confidence when they're busted.

So yeah, if you look up how to clean a disk, you'll probably find an answer like this. An analogue is even baked into the ATA spec: "security erase enhanced". But actually doing a "security erase enhanced" is bizarrely tedious, especially on Windows, so overwriting it is.