Hi Catherine,
Based on the information you've provided, seems like she booked a reservation with Instant Book and then cancelled the reservation.
You should receive an email from Airbnb upon the Cancellation and offer her any refunds available.
If I'm not wrong, you seem to have Flexible Cancellation Policy, where she should receive the full amount back (except Service fees). Therefore, you don't get paid and have nothing to refund her.
Have your guest check their end of the Resolution Center if they could make a claim to request a refund from you.
If they're trying to get the Service fee back, they could try to contact Airbnb but no guarantee they could get that back.
Love,
Helena V.