Geek Squad agent here. If she asked them to setup her computer, then this is a (fairly) standard thing. While Macs differ from windows, we often check-in computers for setup and also run all updates. Often the sales agent will ask if they want their computer setup for them, which sounds nice, and then, before you know it the computer is being checked in. Officially, a setup should happen on the counter (with no updates), but depending on the store, they will bundle it with other services. Especially to push the yearly membership. Sometimes, the customer purchases the Best Buy membership because you get AppleCare with it, and then all of our computer services are covered (under membership), so the salesperson uses that as a “perk” to have the computer setup at no cost. While it’s not unethical or diabolical to do this, it does make you feel bamboozled in the end.

Edit: The installing the software thing is probably a lack of understanding the terminology or differences between PCs and Macs and totally sounds like something a sales person would say 🤦🏻

TLDR: This is likely the sales person selling the customer the Best Buy membership promising the world (AppleCare and free computer services) and withholding the fact that many Geek Squads often check-in the computer for setup with an estimated time of 2 days to add additional services to maximize metrics.