One day before arrival Marina wrote that I needed to have cash in order to pay some extras. It turned out this was 50 euro cleaning fee and some other extras, over 120 euro altogether.
This was very smart malpractice. Guests are in a very weak negotiating position, since it is impossible to find a room in Venice within one day before arrival.
Please be warned that this host does not play fair.
Next time she may ask for 120, 200 for 300 euro extra - and you'll have no other choice but to pay, if you want to have a place to stay.