I don't play pirated games, the convenience of "it just works" and accumulating everything on steam directed me that way quite some time ago.

I've heard lutris and friends should make repacks work.

Edit: also "real games" only don't work because the manufacturer chose to break it. There's nothing special about what AAA does, other than abuse their customers. There's no secret sauce. Only secretive source.

If it's a Windows game, it's still possible to play them via tools like Lutris and Bottles. Sometimes you can just double click the .exe file, and Wine will auto-generate a prefix (i.e. directory where an instance of Wine is stored), and you can play it.

Also, virtually all games are real games. Indie games do not "run on anything," and most indie devs do not target multi-platform support, as that takes extra knowledge and effort. What makes it so Linux can run just about any game is a bunch of dedicated global volunteers who were somewhat recently given a leg up by Valve's Proton.

The only thing she'd have problems with is games that use kernel-anticheat.

Check https://protondb.com/ to see if your games will run and/or what small tweaks you might need.