If I could afford to take the loss, I would probably donate the cake to a shelter (and use the donation when filing taxes) and remake the cake. I would also charge an additional fee ($25? $50?) for the inconvenience of having to remake the cake. The reason for the cancellation was totally out of her control. If I couldn't afford to donate the cake and remake, then I would probably give it to her and let her deal with storage for the following week.