How is Christine Linde essential to A Doll's House?

At first glance, it is tempting to assume that Christine
Linde is essential to the play because she helps the audience "tolerate" Nora's immature
and silly behavior.  The reason for this assumption rests on the fact that Christine
seems to take Nora's annoying behavior quite lightly. In fact, she "mothers" Nora to a
point. This helps the audience admit that there may be something about Nora worth
liking. We just do not know what it is, at first.

However,
on a literary analysis, we realize that Christine is a foil of Nora. Nora is oblivious,
happy-go-lucky, immature, bubbly and unreasonable. Christine has gone through hard
times, and is quite acquainted with the realities of life in every way. She contrasts
Nora quite immensely, which allows the audience to notice the extent to which Nora is
actually living in a fantasy world.

Moreover, Christine is
actually the only character to whom Nora is honest. She is also the only other female
character in the play, which may account for the fact that Nora trusts her as a member
of her own gender more so than she would her own husband, because he is a man.
Therefore, Christine is the character that allows Nora to come out and tell the truth of
what she did for Torval in hopes of getting Christine's own
approval.

Conclusively, Christine brings Nora out of her
world, and into reality. She listens, so Nora speaks. She comforts, so Nora confesses.
She talks about reality, so Nora comes closer to it as well. She is ultimately the only
person who shows a real care for Nora, and presents the characteristics that are unique
of a real best friend.