Nora will decide to leave her family. This is the correct version.
When Nora makes a comment about Anne's job and thinks that she might take care of her children, Nora is planning something. Nora does not finish her idea but it is clear she has something in mind. Anne is the woman who looked after her when she was a girl.
These options are wrong:
-Nora will look beautiful at the ball. This is not the conflict reflected in the excerpt. The conflict is related to the truth: Will her husband learn about it?
-Nora will not leave her children. In fact, she will leave them. Nora gets so furious that she decides not to live with Torvald and his children .
-Nora will stay home from the ball. The ball is not the main conflict.