As you are developing a thesis on how Sophocles, in his "Antigone", portrays Antigone's attitudes towards divine and human law, you might start by looking at another traditional opposition in Greek rhetoric and philosophy, namely the logoi/erga (words/deeds) topos. In other words, rather than just look at what Antigone says about the relationship of divine and human law, examine her actions. At what points in the plot does she violate human decrees? At what point does she violate (or obey) divine law?
The next issue is how you determine what divine laws actually are. If Tiresias says something is a divine law, as someone given a divine gift of prophecy, he can say so authoritatively. But on what grounds does Antigone claim to know divine law?
For a thesis, you could either move in the direction of the words/deeds issue or look at how we know what divine law is (and, given that humans disagree, can we legitimately speak of a monolithic human law?)