Basically the Greeks didn't have "literature" as we define it. Instead they set their cultural store by tragedies and orations. What the question is asking is about semantics, if the Greeks had no expression for literature, or any cultural reverence for it, how can we class something Greek as both literature and culturally relevent. She'll have to discuss taking something out of the concept of its own time; with the Greeks this is particularly relevant for sociological relationships (i.e. can you call the Greeks homosexuals when they had no concept of homosexuality?) There is a lot of literature available in this area if she wants to see some of the arguments. Also she will have to look at how the piece was valued in its own time (after all it must have been to still exist now) and discuss whether or not literature existed in a different way to how we define it today. The Greeks had literature, libraries, universities etc, so she will have to explore what notions they employed, which are comparable to what we would consider today as 'literature.' Hope that helps (and I haven't boggled you!)