We regret that this was an awkward and uncomfortable situation for Ms Calduch, but, unfortunately, it is not up to us which taxes to apply. It is clear from the official site of the City of Rome, below, both in Italian and English, that the guest is to pay this tax on location. We made sure to show this site to Ms Calduch. The tax is mentioned in the Extra Details section of the B&B description on the AirBnB site, but cannot be included in the room rate. We chose not to contact the police at her clear refusal to pay the tax, but did contact AirBnB, who reimbursed us the equivalent of the tax that Ms Calduch did not pay.
It is perfectly clear from the description of the B&B that breakfast is at a nearby cafè. The cafè is open from 6:30am and there is a wide variety of freshly baked pastries available all day long and the use of the vouchers is not restricted to the morning. Coffee/cappuccino/espresso/caffè-latte/tea are made on the spot at any time of the day or evening.