I plan on picking up Cyberpunk 2077 on GOG instead of Steam to support CDPR. My live-in girlfriend wants to play it too but I don't want her earning Achievements on my Account. Can I just log out when she plays or something or do I need to buy a second copy for her? I don't mind doing it, but I have Cerebral Palsy, so my wallet won't like it very much.

You'll probably need 2 accounts, both for achievs and because.. she isn't family.
(btw, IMO she should pay it herself if you have health+money issues)

If the achievements are only tracked using Galaxy (and not in game) then you could quit out of Galaxy and start the game just with it`s EXE file, provided she doesn`t want to collect achievements.

That might not work: in at least some games I can launch the game exe without the client active and still get achievements, even running everything under Wine. I'm not sure how the guts work but presumably the game's Galaxy DLL talks to a Galaxy service process (your account login ID must be coming from somewhere), in which case having Galaxy merely installed and having a login saved would be sufficient.

Considering they're in a relationship and living together, I can't see your point of contention.

I.. may have found the incorrect definition of "live-in girlfriend" lol.

could I possibly install the game on her PC then uninstall Galaxy?

Yes if she is not interested in achievements tell her to launch the .exe file from the installation folder and not run galaxy.

thanks for the help, so glad CDPR gives you freedom with the games you pay to own