Response from Chloë:
If she had arrived on time at the check-in (7pm and not 11:30pm) i could have told her how the front door lock works!
Which, by the way, had never been a problem before with other renters.
Concerning the lightbulbs (you just have to plug in the lamps), the WIFI (i sent her a code for free wifi), the towels (clean under the sink) and the shower, she just had to read the description or watch the pictures of the flat to know how it's made.
And yes, 21m2 is a small flat, but it's also specified in the description!!!!