Multiple users, separate library, no files shown

[TheDreadPirate]

My first guess is permissions. Make sure that the jellyfin user has read and execute permissions to the library folders and read permissions to the files.

If you want to create a sort of curated library for your friend, you can use symlinks in the curated library to point to folders in your existing library. You can limit what your friends library has, but also not have to waste space.