Let her do her cancellation all on her own. She needs to work it out with Airbnb, not with you. I would just stay out of it all together.
And be careful not to agree in case you get a request by her via Airbnb, such as "are you okay with guest so and so cancelling her stay" ?
By saying yes, you might think you are only following the guests wishes, but it will get turned around on you by Airbnb such as that you are the one that cancelled... That way, the guest gets refunded her Airbnb fees, but you get penalized. So you must decline that kind of request.
Any promises of future bookings, etc.. are iffy at best, it gets messy before you know it. At this point, Airbnb has the money, not you, so it's not a refund situation yet from your angle. so I wouldn't go there.