Why do Ella and Emma argue about belonging to the "starving class" in Act One?

Ella and Emma begin arguing about whether or not the family belongs to the starving class in Act One because Ella boils Emma's chicken for the 4-H demonstration. Emma says someone asks before they use the chicken, and Emma says they do not ask if they are starving. Emma yells back that no one in the house is starving, and they do not belong to the starving class since they are feeding their faces inside right now.