It is actually Act V, Scene 1 when Lady Macbeth sleepwalks. She is paranoid with fear and guilt. This has led to an increase in her general anxiety and resulted in her sleepwalking. She mentions Banquo’s murder and alludes to one of the prophecies of the witches that Banquo’s sons will sit on the throne. She does not mention anything about the deaths of Macduff's family.
She never explicitly mentions Duncan’s murder. She alludes to it. The most significant event during her sleepwalking is washing her hands. Her fear and guilt have led her to obsessively wash her hands in her sleep. She is trying to erase the stain of guilt. She mentions she still has the smell of Duncan’s blood on her hands. This is the scene when she utters the famous line, “Out damn spot!” She can’t escape the guilt.