How does Lady Macbeth's character change throughout the play?

Ladyis a
complex character. The main constant in her character is her strong sense of duty. She sees as
her first duty as a wife supporting her husband and being responsible for his success, being a
sort of power behind the throne. On the other hand, an important part of what she understands as
her role as a woman is to be tender, empathetic, and a moral compass. In order to support the
ambitions of a husband too filled with "the milk of human kindness," she must
temporarily suppress or repudiate her feminine nature. In ashe states:

... Come, you spirits

That tend on mortal
thoughts, unsex me here,

And fill me  ... full [o]f direst cruelty.

The contradiction between the strength Ladyneeds to commit evil
acts and her feminine nature drives her insane as the play progresses, and her strength
ultimately gives way to remorse. One could say that in the beginning of the play she succeeds by
strength of will in "unsexing" herself but that her feminine nature (as femininity was
conceived by Shakespeare) eventually reasserts itself as the play
progresses.