The host had unjustified suspicion that we brought more people to the apartment and tried to charge more money for that. Her arguments were based on "black hair on the sofa" and "more used towels than expected". All this was a complete nonsense.
Also, note that late check-in may cost additional 20 euros for you. Be ready to pay 40 euros as a cleaning fee as well.
Otherwise, everything looked ok. The apartment matches the description.