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At the beginning of Ibsen's A Doll's House, Nora is presented as a child-like woman who is almost as much a kid as her own children are. She dresses and acts in ways that will make her husband happy.
However, as the play moves along, we learn that there are hidden strengths within Nora. She sneaks sweets behind Torvald's back, participating in her own little rebellion. She has managed to borrow money (illegal for women in 1879) in order to save her husband's life, and she has been finding ways for some time now to attempt to pay the loan back. She is even manipulative of Torvald in getting extra money from him, by playing the coy child-wife.
Nora starts to have some sense of herself as she asserts herself more strongly against Krogstad's threats, though she still lives in fear that her secret will be disclosed.
Toward the end of the play, Nora becomes overtly resistant to Torvald, as he practically has to drag her back from the masquerade party.
By the end of the story, Nora realizes that Torvald does not love her the way she loves him. When he discovers her secret, he is more concerned about his reputation than what his wife has been through in order to save his life.
In witnessing her husband's behavior, Nora's eyes are opened to Torvald's real character, for the first time in their marriage. She also discovers that she knows very little about herself because she was treated like a child first by her father for all the years she lived in his house, and now in Torvald's home—though she is a wife and mother of three.
The last thing Nora does that shows how much she has changed is making the decision to leave Torvald. Whereas she was petrified of losing him if he found out what she had done, she now realizes that she can leave Torvald, and that while it will be financially and socially disastrous for her, we sense she will survive.