It's inappropriate to raid the food from someone else's house.
Jen has spent the night at her friends house who has to leave for work before she gets up.
Jen wants to have something to eat.
Jen calls and orders a pizza to her friends place.
Jen rummages through her friends fridge and puts together something.
Jen's friend is pleasantly surprised she leaves her the rest of the pizza for when she gets home.
Jen's friend has to go back to the grocery store later because she was going to use those items for dinner.