i do not think it is harsh @Gudrun0
Prospects have the choice between doing a request for information or a request for reservation.
Airbnb insists that if you have special needs , you do a request for information to be sure that the place fit your needs.
When you book and cancel , you are repaid following the host cancellation policy. BUT you are never repaid for the airbnb fees.
Moreover, in your listing it is written 'We have 6 rooms to let - singles, twins, doubles and a large family room that sleeps 4 or more".
To conclude :
- it is written in your listing
- you warned her
- SHE choosed to do a request for reservation instead of a request for information
- SHE did not read the airbnb rules before booking.
All her silly fault. Lesson learned.