"Yes, the girl is eating the bread."
When you are referring to the food itself. It can mean "some". You wouldn't use it in this example as the question specifies "The bread". If it read "The girl is eating bread" or "the girl is eating some bread", you would use "du bread" for both cases. But as it says "the bread" you wouldn't use it here, as "the" is "le" (in this case as bread is a masculine word.)