Even though Macbeth is a fairly strong and brave man, his wife tops him. She is stronger, and more ruthless than her husband. And, she is, and always was, aware of the fact that she would have to push Macbeth to commit the murder of Duncan.
Lady Macbeth and Macbeth have a very peculiar relationship with one another. Lady Macbeth criticizes Macbeth constantly and at times Macbeth can do the same to her. At one point in Act 1, Scene 7 Lady Macbeth calls her husband a coward and somebody who has not yet become a man.
When she says, "And live a coward in thine own esteem, letting 'I dare not' wait upon 'I would', like the poor cat I'th'adage?" and, "When you durst do it, then you were a man." "We fail? But screw your courage to the sticking-place, and we'll not fail." I think that those quotes show that Macbeth and Lady Macbeth do not have an easy relationship.
But, Macbeth also implies that she is a masculine soul living in a female's body. Lady Macbeth manipulates her husband so well that he forgets about any objections he may have had previously. For example, when he hesitates to murder Duncan, she repeatedly bothers him and questions his manhood, which, I think, would probably make any man do almost anything. Throughout the play, or the part I have read, Lady Macbeth seems to stay strong until right after the murder had been done. At this point she begins to fall in the stem of the wine glass and go completely insane. She seemed to have so much ambition before the crime but then she seems as if she had lost it all and became consumed with guilt, just as her husband did. As the...