@Olivia452 if the reservation is subject to automatic penalty-free cancellation under Airbnb's covid19 extenuating circumstances policy, then either you or your guest can cancel it for the outcome you want. However, if Airbnb is not automatically showing you that you have the option of penalty-free cancellation when you click "change or cancel" then it is not, and you should not cancel it, as Airbnb will penalize you.
Normally, you could call Airbnb and ask them to cancel penalty-free since you and the guest agree. But Airbnb is currently unresponsive to both phone and message, so you're not going to get any help from them.
So, under the circumstances, the guest should cancel, then you should accept the option to refund them in full when you get the cancellation notice. Unfortunately, the guest's Airbnb fees will not be refunded in this scenario. You, or the guest, can pursue this with Airbnb, but you're unlikely to have any short-term success, based on my recent experiences and those of others.