This may come across harsher than it would if we were talking but I tend not to beat around the bush.
You have been a SH for 4 years but do not know what cancellation policies you use?
Why did you contact AirBnB at all, she asked what would happen, not uncommon, I tell Guests in such case that the sooner they cancel the better, I tend to assume that they are going to anyway and that opens my calendar up quicker.
If they ask about the finacial side I copy the AirBnB terms and send it to them. When doing so I decide if I want to offer them anything extra, if the booking is a long way out or they booked and realised quickly they made a mistake I tell them I will refund what I would get IF they cancel quickly. Otherwise I may say nothing or I will refund if I get another booking.
As soon as you involve ABB you lose control, who knows what they will do or not do.
A booking is not a booking until it is booked, likewise a cancellation is not a cancellation until you have it confirmed.
Last week somebody messaged me that they were not coming for a one nighter but never cancelled so I was still ready, might have got another message saying all was good and they were coming.
David