This is a really interesting question. I don't know if she is more virtuous than Antigone, initially she is submissive to Creon's demands. She is the "good girl" of the family. She is reasonable and understands her place; she is carries out Creon's orders and attempts to convince her sister not to follow through with her act of rebellion. In many ways Ismene is Antigone's foil. She not only highlights Antigone’s heroism she ultimately begs Antigone if she can follow in her footsteps. So, is Ismene more heroic? I can accept that. True self discovery leading to self sacrifice is what separates heroes from mere mortals like myself. In the end she not only understood her sister's convictions, she adopted them as well.