How does Lady Macbeth swap roles with her husband?

What Macbeth lacks in decisiveness, Lady Macbeth makes up for in bloodthirsty lust for power and wealth. Swearing off her femininity at the beginning of the play, Lady Macbeth manipulates her husband powerfully to follow through with his plans to kill Duncan. After the act of regicide, it is Lady Macbeth who has the soundness of mind to plant the incriminating evidence on Duncan's guards. And yet, her firmness disintegrates gradually as the play progresses, leading to nightmares that haunt her and ultimately drive her to suicide. In this regard, Lady Macbeth appears to switch characters with Macbeth midway through the play. Although most famous for her cruelty and lines such as "unsex me here," the decline of Lady Macbeth is also of great interest and certainly a mysterious aspect of Macbeth.