On Act 5 Lady Macbeth begins her slow descent into insanity, brought in by the guilt of the deaths caused by her evil influence. Her insanity manifested itself in the form of sleepwalking, and her hallucinations of seeing blood on her hands.
It would have been more interesting, in my opinion, to see her actually pay for her wrong doings more actively than so passively. She is merely sleepwalking off her guilt and she seems reduced to a sleepy crazy woman. As bad as her character is, she should have had a couple of scenes in which she receives physical punishment for being so bad. At times it is tempting to imagine Macbeth himself squaring her off and making her feel as bad as she is. Yet, I do agree that her character is powerful and strong enough to "take it like a man" and, in addition to just sleepwalking and going crazy, she could have gotten a couple of smack downs that would make her cry really hard and possibly become more human prior to losing her mind. But then again, who are we to argue with Shakespeare? If he did it, he did it for a good reason, because he is the master...the Bard.
I do not fully agree with the answer posted here. Lady Macbeth, in my opinion, should not be seen as a wicked and fiendish woman. To see her and Macbeth like that is to do injustice to the moral nuances which are at the core of this play. In a play, which is so centrally about the indistinctions between good and evil and about the mutual convertibility of the two, one should not reduce Lady Macbeth to a witch-like figure at all.
In my opinion, she too, like Macbeth is a tragic character and hers is primarily a tragedy of love. It is her desire to be more important to Macbeth and of course to see her husband as the king that she does all this. But ironically enough, the crowning only alienates her from Macbeth, as she poignantly admits in the 'nought's had all's spent' speech.
The sleep-walikng scene, I think, makes the audience feel sympathetic towards her. Her sad ruined state of mind is painfully tragic indeed. As for the psychological suffering as a passive suffering, I do not think so. In the modern age of psychoanalysis, I do not think calling psychological suffering 'passive' is tenable at all.
If she is made to suffer in the mind and Macbeth in the body, that further attests Freud's basic thesis about the couple as representations of two different aspects of a unitary being.
It was Macbeth who had done the deed and Lady Macbeth had planned it for him. So, in the very nature of their contributions to the crime, there was always the physical-mental ratio, if I may put it like that.