Merry Christmas @Valerie3,
You have your listing's cancellation policy set at moderate so if they cancel, they will receive some refund. Here is what the moderate cancellation states for people leaving early: If the guest arrives and decides to leave early, the nights not spent 24 hours after the cancellation occurs are 50% refunded.
I hope this helps answer your question. In any event, you would not be the person refunding them money but Airbnb would reimburse them. Yes it will come out of your pocket but you should not have to deal with it.
Cheers
Dave
David
Superhost Ambassador ~ Host Club Community Leader ~ Community Expert ~ Experienced Co-Host