Hello @Cheryl413
It does seem unfair that you risk getting a bad review because this person decided to go for the cheaper non refundable offer and yet now expects a refund because of a hitch.
As @Mike-And-Jane0 suggest, get the guest to cancel herself, definitely not you and you can say that she will get the cleaning fee back at the very least (if you have one of course) and you will refund her if you get a booking for her dates booked.
If this person does leave you a bad review, you will be able to give your side of the story which will show up against hers.
All the best
Joëlle