Antigone's suicide makes her believe that she is stronger as a character. She prevails over Creon because she believes that what she has done in burying her brother makes her better than Creon, and the Gods will favor her in the after life.
I scorn them not, but to defy the State
Or break her ordinance I have no skill.
A specious pretext. I will go alone
To lap my dearest brother in the grave.
My poor, fond sister, how I fear for thee!
O waste no fears on me; look to thyself. (82-85)
This quote shows Antiogne's strength prior to the suicide. She was a strong woman, looking to become even more empowered. She has been a shrewed study of politics, human psychology, and on top of that she feels a moral and righteous justiication in what she is about to do. her suicide cements her wishes and she has, at least to her way of thinking, the last laugh.