@Howard42
Howard, please don't be torn on this issue, refund the guest! Look at it this way, you had to prepare the listing anyway, she has not arrived and used anything. The only thing is you may have missed out on an alternate booking for the night. Believe me the goodwill you generate will come back to you mate!
Here is a post I made the other day about exactly the same situation as you.
https://community.withairbnb.com/t5/Hosting/How-great-is-Airbnb-s-service/m-p/852450#M208675
I had to actually ask CX to refund the guest because the cancellation was for the day the stay was to commence. Howard, sometimes we just have to take a hit, but, in reality you will feel a better human being for doing it....and isn't that is what life is all about, being a better human being!
Cheers......Rob
PS:....Here is the review for that failed stay......