@Inna22 I have to say, you do get some of the weirdest guests. Of course no one saves food that is left behind, unless it's unopened stuff and the host or the cleaner takes it home. What, does she want you to pack it up and send it to her?
Tell her that as it's a whole house listing, your cleaners are instructed to throw away anything left in the fridge, as guests are reminded to take all food with them that they want, so the assumption is that anything left is unwanted. Ask her how she would have felt about checking in to find that the previous guests' leftover, opened packages of food were in the fridge?
Was this the bride?