Question

the excerpt from " The Royal House of Thebes ."

Antigone and Ismene heard with horror what Creon had decided. To Ismene, shocking as it was, overwhelming her with anguish for the pitiful dead body and the lonely, homeless soul, it seemed, nevertheless, that nothing could be done except to acquiesce [to accept without protest]. She and Antigone were utterly alone. All Thebes was exulting that the man who had brought war upon them should be thus terribly punished. "We are women," she told her sister. "We must obey. We have no strength to defy the State." "Choose your own part," Antigone said. "I go to bury the brother I love." "You are not strong enough," Ismene cried. "Why, then when my strength fails," Antigone answered, "I will give up." She left her sister; Ismene dared not follow her.

What makes Antigone a rebel?

her statement that women are not strong enough to defy the state
her horror at what Creon had decided regarding her brother's burial
her decision to go bury her brother, with or without Ismene
her admonition to Ismene to do whatever she chooses

Answer 1

Her decision to go bury her brother, with or without Ismene.

That action directly defies Creon’s edict and shows she will honor family/divine duty rather than obey the state, even if she must act alone.