How does Shakespeare present good and bad in his characterization of Lady Macbeth?

Shakespeare presents both the good and bad sides of Lady Macbeth's character by showing his audience what she is like when she's alone, or when she thinks she's alone, because that is when she can be her true self without attempting to hide or persuade.  

First, in her response to Macbeth's letter in Act 1, Scene 5, we see some of her worst qualities displayed.  She is manipulative, wishing her husband home so that...

Shakespeare presents both the good and bad sides of Lady Macbeth's character by showing his audience what she is like when she's alone, or when she thinks she's alone, because that is when she can be her true self without attempting to hide or persuade.  

First, in her response to Macbeth's letter in Act 1, Scene 5, we see some of her worst qualities displayed.  She is manipulative, wishing her husband home so that she can "pour [her] spirits in [his] ear" and coerce him to commit to the violence she plots against the king (1.5.29).  Her concern that he is "too full o' th' milk of human kindness" to commit such violence without her coercion shows that she lacks (or wishes to lack) such kindness or compassion (1.5.17).  Lady Macbeth jumps to murder right away, whereas it took Macbeth some time to consider it.  She calls Duncan's arrival at their house his "fatal entrance," indicating that she has already begun to plot his murder (1.5.46).  Finally, she begs for deadly spirits to "fill [her] from the crown to the toe top-full / Of direst cruelty" so that she can advance her plan without emotion or hesitation (1.5.49-50).  Her speech while alone on stage shows her to be ruthless, deadly, and ambitious to the point of avarice.  

Second, in her sleepwalking scene, when she is unaware of the presence of others, we see an unadulterated version of Lady Macbeth as well.  Here, we can tell that she does, in fact, have a conscience and that she does feel incredibly guilty.  She imagines that she cannot wash Duncan's blood from her hands, crying, "Out, damned spot, out, I say!" (5.1.37).  Moreover, she obviously regrets the monster that she helped to create out of her once-kind husband, Macbeth, as she laments the death of Macduff's wife and children:  "The Thane of Fife had a wife.  Where is / she now?" (5.1.44-45).  These were senseless murders by which Macbeth had nothing to gain.  His ruthlessness is the result of Lady Macbeth's shaming and prodding of him.  He was not so before.  Her ability now to feel regret, compassion, and guilt, shows us her softer side, the side of herself that she attempted to hide when she prayed for manlike strength and mercilessness prior to Duncan's murder.