Do you have a Mod-Cheat installed in the game?. Because I've only used cheats on its console, and I haven't had so many problems with triggering the events. And if you use cheats, you only modify some values, but the events are triggered by the game code. But with a Mod-Cheat that is not updated, your code can break the game when it should trigger an event.
To find Carol in the room C4, you don't have to go to the Library when Ruby is reading a book on a bench, because in that case the ones that always appear in the room C4 are Tanya & Vanessa (when it's not empty).
Also, when you go to ask that book for Elena, the one who is sitting next to Carol in that event in the room C4 of the Library, is Ruby.
If you can't trigger that event for some reason, and want to force it with a cheat. Open the console in the game and type this command:
jump CarolYRubiBiblioteca
If you don't have the console enabled in the game, here's how to do it:
https://f95zone.to/threads/bastard-girls-r-v1-7-2-leocid2.33364/post-2501365
to close the console type
exit and press Enter
And to find the others two books use this walkthrough: