How does Lady Macbeth react to her husbands guilty conscience?
Her initial response is to demean him and question his manhood. She suggests he is childish, saying "'tis the very eye of childhood that fears a painted devil." When he sees the ghost of Banquo (a product, some would say, of his guilty conscience), she asks him if he is "a man", the implication being that he is not. Later on, she actually says he is "unmanned in folly."
Then she chides him (O proper stuff) and says that what he imagines is a product (the very painting) of his fear, suggesting he has given in to cowardess. Indeed, she goes even further and suggests his behaviour would be more appropriate for an old woman,telling tales around the fire, than for a man.
Her second response, however, is to cover for him. She reminds him of his place and of the actions expected of him. She makes excuses. She faints (I'm assuming here that he talks and blunders in his explanations about why he's killed the guards out of guilt). All of these actions are strangely protective--they attempt to create an appearance of normalcy and to shift the focus away from him.
I believe you are referring to the first act when Macbeth is struggling with the idea of killing the king. Lady Macbeth attacks his manhood, telling him he is less than a man if he cannot go through with the murder. At this point, Macbeth and Lady Macbeth are a happily married couple, and she is able to convince him to go through with the murder. Her ambitions for Macbeth are as great as his, if not greater.
Throughout the course of their actions, she even goes so far as to wish that she were the man of the family. It would have been the ultimate insult as a Scottish Lord - your wife not only questioning your own masculinity, but then wishing it upon herself in order to complete a deed. It's no wonder Macbeth felt like he couldn't back out...
Lady Macbeth, having assumed the more masculine and dominating role in their relationship, reacts to her husband's guilty conscience in certainlly dramatic ways.
1) After having contemplated over the issue of assassinating King Duncan, and having deicded that it were best he did not go ahead with the deed, Macbeth faces an angered Lady Macbeth who immediately question his manhood and the art of keeping his word. She compares him to herself and says that if she had said so, she would have 'dashed the brains' of the 'babe' that suckles her breat. SDhe also calls him 'green' and a 'cat' that wants the fish but is afraid of getting its feet wet. This bears witness of her innate strength, eradiction of all feminity and feeling of remorse and ambition.
2) After Duncan's murder, a scared and uncertain Macbeth forgets to place the bloody daggers near the chamberlains as instructed by his wife. When his wife asks him to go and keep them back, he refuses for fear of having to look at King Duncan's face again. To this Lady Macbeth compares him to a child who was scared of looking at pictures and dead objects that can cause no eminent harm on to an onlooker.
3)When Macbeth hallucinates about Banquo's ghost at the feast laid out for all the ranks in his kingdom, it not only startles his guests but symbolizes his guilt and insecurity. The callous man, bold and fearless when it comes to the battlefield is easily manipulated by supernatural elements which include the witches. To this, Lady Macbeth to question his manhood yet again, and snap out of his apparent trance.