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.