In addition to the valuable info @Steve143 gave, you may copy this from the Airbnb help guide, so it is clear to the guest that the security deposit never got taken out of her account in the first place, as I assume you didn't file a claim, and/or 14 days have passed. That should reassure her, no need to even call Airbnb.
here it is, sorry that on mobile I couln't copy the link to it:
What happens if a host makes a claim on my security deposit?
When you book a listing with a security deposit, your payment details are stored but not charged or authorised for the deposit unless the host makes a claim. The host has 14 days from your checkout date to make a claim on the deposit for damages to their property.