Where in Macbeth does Lady Macbeth sleepwalk and talk?
The scene you want to look at is Act V scene 1, which moves the action away from Macbeth and his approaching conflict with Malcolm and Macduff for one moment to have a look at another human tragedy of the events of the play. The Gentlewoman and Doctor that we are persented with discuss the condition of Lady Macbeth, and then she is shown to enter, sleepwalking, making obvious reference in what she says to her and her husband's involvement in the murder of Duncan:
Yet who would have thought the old man to have had so much blood in him?
It is clear that this amounts to a confession of her and her husband's murder of Duncan, yet at the same time the way that she is acting speaks of the impact that her guilt has had upon her and how she is plagued by the way that she abandoned herself to evil so quickly in Act I of the play when she first heard of the prophecy of the witches.