Guest cancelled, but payment received! How to return payment?

[Ann16]

A guest, who I have hosted previously and therefore know, needed to cancel a reservation.  She let me know within my allowable cancellation policy (even asked me if it was ok!)  I, of course, said yes.  She cancelled (within the allowable time).  I received the cancellation notice from Airbnb. 

However, I also received payment!

How do I return the money to the guest?  

[Ann16]

Oh, and airbnb keeps telling me I need to review this guest, even though it shows up as a cancelled reservation.....