When you analyze the play A Doll's House under the focal point of "marriage", you can see that the character of Mrs. Linde, complete with her, widowhood, her current issues, and her life story, serve as a foil to the marriage, issues, and life story of Nora Helmer.
This is significant because it is through Mrs. Linde that the audience can finally learn about the reality of Nora's marriage. When Nora describes the dynamics of her relationship with Torvald, it is Mrs. Linde who suggests that Nora should just come out with the information about Krogtad's deal. In Mrs. Linde's own words the the best thing to happen between Torvald and Nora is that, for once, one of them acts realistically about something.
Mrs. Linde is correct: already we see that, not once, does Helmer refer to Nora as anything else than a pet, or a toy. In an enabling manner, Nora responds back by enacting the part quite masterfully. The denial and the acting only look like solid ties that keep Nora and Torvald in good and candid terms. In reality, however, this tendency to push down reality and only show a good face only continues to detour any chance of Nora and Torvald ever getting to know who they really are.
Therefore, in A Doll's House, the main contribution to the strength of the marriage between Torvald and Nora is that they accept each other by who they really are, and not by what society dictates that they should be, or should act like. If Torvald removed himself from his own grandeur as a high society success, he would have seen his wife's real persona. He could have even learned to appreciate the sacrifices that she had done for his health. It is precisely that erroneous idea of marriage as a sign of social success what makes the Helmers have to create masks to hide who they are, not only from society, but from each other.