• Lady Macbeth's words are filled with panic and imagery (blood, sleep, hand, dagger, water, and sound imagery), all of which show signs of guilt, paranoia, and signs of mental illness.
• Lady Macbeth observes that she would have done the deed herself “If Duncan hadn’t looked so much like [her] father as he slept.” (She has a weakness, but acts “tough,” so she suffers from gender identification problems).
• Lady Macbeth, after chastising her husband as a “weak-willed creature,” plants the dagger and returns… now just as bloody as her husband.
• She shows much paranoia and guilt, all related to hearing strange noises: "Who was it that thus cried? Why, worthy thane..."
• She uses much "fluids" imagery (water to wash the blood): "Go get some water, And wash this filthy witness from your hand."
• Also, the hand and dagger imagery runs throughout.

Why did you bring these daggers from the place?
They must lie there: go carry them; and smear
The sleepy grooms with blood.

• And, finally, her words are filled with sleep imagery.  Remember, the Macbeths have murdered sleep, and Lady Macbeth will not be able to sleep from here on, another sign of guilt and mental illness.

The scene opens with Lady Macbeth's declaration that she has succeeded in getting the guards drunk and they've fallen asleep.  Then there is the confusion immediately following Macbeth's murder of Duncan.  Macbeth hears sounds and voices and isn't sure where they are coming from.  Lady Macbeth doesn't hear the voices and doesn't understand why Macbeth does.  When he asks what she heard she says she only heard the owl scream and the crickets cry.  The use of these images and words is fitting because they reflect the horror of what has just happened.  Both "scream" and "cry" are appropriate.  Most of the time, in the part that follows, Lady Macbeth is trying to bolster Macbeth and to get him to see the wisdom of their deed and to understand what steps are next.  She tells him to ignore the voices he heard and warns him that to dwell on them and the murder will drive them mad.  That, of course, is irony and foreshadowing.  She chastises Macbeth when she realizes he still has the bloody daggers and that he hasn't washed the blood from his hands. The tells him she is made of sterner stuff "...shame to wear a heart so white."  The irony of the all her tough talk is that she is the one who goes mad and can no longer stand the guilt of what they've done.