Lady Macbeth goes through three stages: excitement, determination, and guilt.
When Lady Macbeth first hears about her husband’s prophecy, she gets excited. She wants him to be king.
Glamis thou art, and Cawdor, and shalt be
What thou art promised. Yet do I fear thy nature;
It is too full o’ the milk of human kindness(15)
To catch the nearest way. (Act 1, Scene 5, p. 19)
Although Lady Macbeth is excited, she is still worried that her husband will not rise to the change. She thinks he is too nice a person to do what has to be done to take care of King Duncan.
Thy letters have transported me beyond
This ignorant present, and I feel now
The future in the instant. (Act 1, Scene 5, p. 20)
Yet when Macbeth arrives, she is positively giddy with excitement. She makes some quite spooky speeches as she tries to stir up his ambition, describing how she has nursed a baby and she would gladly bash its brains out.
Lady Macbeth’s second stage is determination. She gets her husband all worked up and ready to commit murder, but then he backs down. She will have none of it. She convinces him.
But screw your courage to the sticking-place,
And we'll not fail. (Act 1, Scene 5, p. 24)
Macbeth has second thoughts, but she continues with the plan. It is her bell that calls him when he is talking to his floating dagger. She also scolds him for not following the plan exactly.
Why did you bring these daggers from the place?
They must lie there. Go carry them, and smear
The sleepy grooms with blood. (Act 2, Scene 2, p. 30)
Even after Macbeth kills Duncan, they are not safe. When her husband starts acting crazy, talking to the ghost of Banquo at the dinner party, Lady Macbeth again takes action. She is determined to keep her place now that she has it.
Sit, worthy friends; my lord is often thus,(65)
And hath been from his youth. Pray you, keep seat.
The fit is momentary; upon a thought
He will again be well. (Act 3, Scene 4, p. 51)
Lady Macbeth is very interested in keeping up appearances. She manages to do so until Macbeth’s behavior gets so weird that she has to dismiss the guests. It’s the beginning of the end for Lady Macbeth.
The third stage Lady Macbeth goes through is guilt. She feels that she is to blame for Duncan’s murder, and the murders that followed.
What need we fear who knows it,
when none can call our power to account? Yet who would
have thought the old man to have had so much blood in
him? (Act 5, Scene 1, p. 77)
Lady Macbeth is unable to wash the blood off her hands, because this time the blood is figurative and not literal. She succumbs to grief and guilt, and kills herself.