I too was brought up not to waste food.
I have managed to master the art of buying a quantity of anything that I know we can eat while it is still good.
Any meat, fish or milk that gets pushed to the back of the fridge and forgotten is offered to the cat. If he refuses it, it goes into the bin., Old vegetables into the compost, except for potatoes that I will consider planting in the garden once we no longer have frost at night.
We are constantly bombarded with information about the world's resources being used up too fast due to our carelessness, so throwing food out should be considered in this light, surely.
Public health authorities insist that food that has been served in a cafeteria or dining-room in care homes, hospitals and businesses must not be used again, so I suspect this has coloured your daughter's thinking.
I do not think the rule needs to be followed in private home, as long as those who prepare food, or put it away, remember to wash hands first.
I was taught that all food should be kept in boxes with tight fitting lids, as I am certain you were too, and never left in the packaging or the tins it was sold in.