Hello @Sanderien0,
If the booking was for 28 dyas or more then the long term cancellation policy is automatically applied by Airbnb independent of your normal policy.
The long term policy says that the guest must pay for the first month if they cancel before arrival. So if she books for a month and cancels before arrival she will not be refunded by Airbnb. See the long term policy.
You can refund her the full amount but it will probably be charged to your credit card immediately as you've not yet been paid by Airbnb.
Some hosts chat to the guest and suggest that they will refund an amount for any days that they can book after the cancellation.
So if you received bookings for 1/2 the month you could refund her that amount when you get paid in October. If you refund after you've been paid Airbnb will arrange the refund, not by charging it to your card, but by deducting it from any payouts due to you in October and afterwards. For example, if you refund her €500 next October and then you get a booking in November for €600 then Airbnb will pay you only €100 for that.
As the long term policy applies, she won't get a double refund if you refund her through the resolution centre.
Check the post "Contact Airbnb: A Community Help Guide" for ways to contact Airbnb customer service.
You can find it by typing "contact airbnb" in the "Search the community" box on these help forum pages where you posted your question. Suggestions will appear as you type. Click on the "Contact Airbnb: A community Help Guide" one.
Steve.