Lady Macbeth certainly expresses anxiety elsewhere in the play, but seems almost cold-blooded in her response to the murders in Act 2, Scene 2. When Macbeth expresses sympathy for his victims, she chastises him:
Why worthy thane, you do unbend your noble strength to think so brainsickly of things. Go get some water and wash this filthy witness from your hands...
Her only fear emerges early in the scene when she briefly thinks that Macbeth has been unsuccessful in his attempt to murder Duncan.
Macduff seems not to suspect Macbeth in Act 2, Scene 3. In fact, he discovers the bodies, and does not really question Macbeth's explanation that he killed the bodyguards. He is terribly shaken by the death of Duncan, and immediately swears himself, as indeed does Macbeth, to avenge the murder. It is only in the next scene, when he makes it clear that he will be returning to Fife rather than attending Macbeth's coronation, that some degree of suspicion is intimated to the audience.