Yes, you will have to deduct those days IMO. She is paying for the spot and it needs to be available to her. It is no longer available to her so you will need to refund that money. Or you could cancel your plans.

My first 2 Christmases were like this. I was closed for the whole week as no one was booked in but because I charged for those days, I had to be available if someone decided they needed/wanted care. I did inform them that I'd need 2 days notice though because I would be out of town and staying out of town if no one came. Thankfully no one needed care!

If they are paying for the spot, the option to come needs to be available.