What changes are seen in Lady Macbeth in act 3 scene 2?

In Act 3, scene 2 of Macbeth, Lady Macbeth and Macbeth begin to be afraid and unhappy about Macbeth's murder of Duncan. She says at the beginning of the scene: "Naught's had, all's spent/Where our desire is got without consent/'Tis safer to be that which we destroy/Than by destruction dwell in doubtful joy" (lines 6-9). In other words, she and Macbeth have gained nothing, or naught, when they have spent or risked all to...

In Act 3, scene 2 of Macbeth, Lady Macbeth and Macbeth begin to be afraid and unhappy about Macbeth's murder of Duncan. She says at the beginning of the scene: "Naught's had, all's spent/Where our desire is got without consent/'Tis safer to be that which we destroy/Than by destruction dwell in doubtful joy" (lines 6-9). In other words, she and Macbeth have gained nothing, or naught, when they have spent or risked all to kill Duncan, as their "desire," or Macbeth's attainment of the crown, is achieved through wrong means. She thinks it safer to be like the dead king than to live with "doubtful joy," or a troubled existence. 

By this point in the play, she is clearly regretting the doubt and uncertainly in which she and her husband must live after the regicide. However, she has not yet become insane, and, later in the scene, she instructs her husband to pretend everything is normal, even though he is also starting to be afraid. Macbeth is frightened that Banquo knows he has killed the king, and Lady Macbeth tells Macbeth to "sleek o'er your rugged looks. Be bright and jovial/Among your guests tonight" (lines 31-32). In other words, she instructs him to neaten himself up and act happy when people come to the castle that night. Macbeth is already plotting to kill Banquo, but he does not tell Lady Macbeth at this point. Instead, he says, "Be innocent of the knowledge, dearest chuck,/Till thou applaud the deed" (lines 51-52). In other words, he says that she won't know what he's planning until she sees Banquo is dead at his hand. At this point in the play, Lady Macbeth is turning to doubt, but she has not lost her mind yet.