@Isabelle1793 A guest's account getting hacked is none of a host's affair. That's for a guest to work out with Airbnb. Nor do you have any way of knowing if that is true- she was probably lying in order to get you to cancel so she wouldn't lose money if she cancelled.
If a guest wants to cancel, they need to cancel from their end. Reasons for a host to cancel are only if a host is unable to fulfill the booking for some reason. The host got sick or injured, the unit got flooded or is otherwise uninhabitable, etc.
Maybe Airbnb will lift the penalties if you plead ignorance and explain, as Colleen suggested.