Good of you to be understanding to guests issue. (And apologies in advance readers - I am on mobile app and it will not allow me to change anything once I type past 4-5 lines.... so I have added this to apologize for upcoming spelling mistake of 'reboot' which was meant to be 'rebook'! Aghh!)
So you may want to consider changing your cancellation status from strict to moderate - general experience shows that most guests don't change their minds once they book and it gives you more flexibility to help out in situations like this one.
This really is the guests problem to deal with. But if you insist on getting involved - tell her to cancel, accept the fees paid, and then issue her a refund less any Airbnb fees (which should be guests 'penalty' (or yours?) for cancelling a 'strict' booking. Assuming she reboots with you - and if she doesn't you still be able to decide how much of the cancellation fees you refund.
hope this helps!