My guest wants to cancel 2 days into a 5 day reservation.

[Jacinto11]

So my guest tried using ANOTHER BOOKING APP and suddenly got her 1 place booked both on airbnb and another booking app. As a result she went to me to book her guest from the OTHER BOOKING APP just so she can accommodate the guest. The guest never arrived and cancelled on her past midnight of day 1 (so that's technically day 2). On the afternoon of day 2 she said her parents may stay instead but in the evening of day 2 her parts informed her that they can't use the my place either. My cancellation policy is set on strict and I understand I can't cancel her booking otherwise I'll get penalized, what should we do?