Hi Valer1a1,
If you'd like to share folders with another user on your Mac, these steps might help.
What sort of user is your girlfriend set up as? Is it a guest user? If so, check that the setting quoted below:
Guests can access shared folders on your Mac. To turn off guest access, deselect “Allow guest users to connect to shared folders” in the Guest Account pane of Users & Groups preferences. See Set up users, guests, and groups.
In your case, you'll want to make sure the checkbox is ticked for "Allow guest users to connect to shared folders." The information above is from Set up file sharing on Mac. This link also has other guidance about file sharing that could be helpful to you. If the issue remains, let the community know what kind of user your girlfriend is set up as and what troubleshooting you've already tried (restarts, etc.) Also, please provide a translation of the screenshots in this post or any future screenshots.
We hope that helps with your question and take care!