If I told her to install Windows, she'd at least know what to tell the technician in the event that I'm not around.

If I install Pop OS on her computer she will just tell the technician she has a laptop because she doesn't know the difference. I would hope that the technician does know the difference, and moreover, knows how to use it (which I assume someone calling themselves a technician would know how to troubleshoot basic stuff on a foreign operating system, but I've been wrong on lighter assumptions)