In this particular scene—scene 2—Antigone has just openly admitted to Creon's face that she's defied his express order not to bury her dead brother Polynices. This is in response to Creon's direct question as to whether she avows or disavows the deed.
There was never any doubt that Antigone would so defy Creon, nor was there any doubt that she would give an honest answer to Creon's question when challenged about it. This particular scene tells us everything we need to know about Antigone's personality, especially her bravery, honesty, and stubborn fidelity to the principles of cosmic justice.
The scene also tells us a lot about Creon. He's furious at Antigone's defiance. As king, his word is law, and he regards it as a personal insult to have one of his subjects make a mockery of his most recent proclamation. For good measure, he challenges Antigone, asking her if she doesn't feel ashamed for standing apart from the rest of society in defying her king. The two then engage in a brief back-and-forth, which ends with Creon asserting that no woman will ever rule him.
Just afterwards, Antigone's sister Ismene enters the scene. Immediately, she claims to have helped Antigone bury Polynices. It's not true, of course, but Ismene expresses her wish to share the burden of the terrible fate that Creon has in store for Antigone.
One might have thought that Antigone would be thankful to her sister for expressing herself in such noble terms, but Antigone has no need for the solidarity of the word, only of action. It's not enough for Ismene to say that she's prepared to share Antigone's fate; she should've actually helped her sister perform the deed. But she didn't, out of fear of what Creon might do to her. It's too late, then, for Ismene to take responsibility for something she didn't do.