You guys are heartless for giving this person such a hard time. It's nearly impossible to just "make things stretch" when you're already living paycheck to paycheck as they seem to be doing. Shame on you all.
Minniex, my advice is to ration out your food. Can you all each eat only breakfast and dinner so that your food lasts longer? Even if you can't do that, plan out your meals ahead of time so that you know exactly what you have, what you'll be using, and when it'll be gone. Also in the store, think: what can you buy for cheap that still makes a bunch and can be eaten as leftovers too? Soups and stews are good for this. Foods and pastas in boxes that you make just by boiling in water aren't the best for you but they'll fill you up. Bananas expand to twice their size in your stomach so they'll fill you up too. Bread can be eaten by itself if you're desperate.
See if there's any soup kitchens or food lines near you. Churches will also sometimes have things like this - if not, they might know of a different church or organization that does. It doesn't hurt to ask. Good luck, I hope you are all okay.