Yeah, it's currently a bit confusing. I think it would be better to just package the rpy files in the girlpacks, and (if you want to keep that versatility) offer different versions of the BK.ini files to "choose what events you want to enable".
1_events.rpy contains custom events for when she is a slave, 2_events.rpy contains custom events for when she is in the city. But more importantly, the BK.ini tells the game what custom events it should use! (which is all of them with the current BK.ini, so you must download all .rpy files)
For example, under [background story] for Rem, you'll find city_label = "Rem_City_Life". That means the game will try to activate this event whenever you encounter her in the city, even if you haven't downloaded 2_events.rpy (in which case you would run into an error)
It's not about choosing which .rpy files to download, but about choosing which events you enable in the BK.ini - the game won't mind one bit if your girlfolder contains some .rpy files with events that are never activated, but it will bash its head into a wall if you're saying there's an event (or a label, to use the code's terminology) in the BK.ini which it cannot find in any .rpy files
To disable certain events in the BK.ini, simply comment out those lines like so ## city_label = "Rem_City_Life"
