Re:
If your wife is like mine and not very technical, just make sure Defender and the firewall is set up, also make sure updates are taken care of automatically and she should be fine, most viruses tend to lurk around on porn and file swapping sites so she should be OK.
Yes, Windows has become very resistant to remote attacks and defends very well against your typical viruses, worms and trojans. Those account for no more than 20% of the security threat however. Windows (desktop OS) is still nowhere near secure, and it never will be.
Millions of users still regularly install software that reconfigures their internet search provider, includes legal spyware, or a service which just occasionally "borrows" their PC to send spam to a couple thousand random mail addresses. None ot those things are easily detected by anti-malware software, as they aren't out to destroy or control your system. They only use functionality that every other piece of productivity software might also use, but they are nevertheless crapware. That is how millions of users screw up their PC, not to mention when users unintentionally delete files they shouldn't, or don't update software packages they should (adobe flash was a nightmare in that regard).
Particularly those looking for free software are at risk, like the RT download the OP linked to. If that happens to be a malware infected version if Windows, then the OP is screwed, as such malware is virtually impossible to detect.
Requiring that all software installations occur through an app store, that is curated by experts, and deemphasizing the importance of the file system, solves a lot of those problems. Unfortunately, those problems will plague Windows (desktop OS) to the end of its days.