@John6181
You can open the dates.
Either the guest cancels. They will still get charged for the entire stay according to the long term cancellation policy, but you can refund them any rebooked nights.
Or, you send the guest an alteration request with the dates changed to end the stay a week earlier. Again, according to the long term cancellation policy, they should still be charged for the full first month but you can refund rebooked dates. The guest needs to accept the alteration request for it to go through, so in both cases, you need to work with the guest. You can't just do it by yourself.
Just bear in mind that they might not get all their Airbnb fees back and, personally, I don't think you should pay these out of your own pocket for rebooked nights as Airbnb, not you, will be receiving the fees.