So what? She can run linux on mac, can't she? I run linux on my macbook, but I still keep macOS and occasionally boot into macOs to update my TOMTOM navi. Or to test whether a particular program runs on Mac, to check the possibility that the reason it does not work me is because I have Slackware. To be fair, I got the macbook from my employer. Otherwise I would buy a ThinkPad or Dell. But many physicists do use macbooks, and it really nice to have a well supported system at hand even for someone who almost always runs Linux.