We may or may not believe that Lady Macbeth's mental destruction resulted from her weakness because she was a woman, but that idea is found within the play. When she first begins planning Duncan's murder, Lady Macbeth calls upon the spirits to "unsex" her so that she might be able to carry out such a horrible deed. In her plea, she seeks to have her "womanly" qualities replaced by the sterner masculine ones. Her speech establishes the idea immediately in the play that a woman, unless she were significantly changed, could not stand up to the cruel acts that would follow.
The first sign that Lady Macbeth is not as cold as she would like to be occurs when she returns from Duncan's chamber, after laying out the daggers Macbeth will use to kill the king. She tells her husband that she would have killed Duncan herself, but in his sleep, he looked too much like her father.
After Duncan's murder, she struggles to hold her husband together as he struggles with fear and guilt, but there is no one to help her with her own feelings, which she effectively buries in her efforts to help Macbeth retain power. Her own guilt surfaces with a vengeance in Act V as she walks in her sleep, tries to wash the psychological blood from her hands, and moans pitifully. Afraid of the dark and tormented by guilt, she finally takes her own life. Does she come apart because she is a woman? Within the context of the play, it seems so. In contrast, Macbeth, the strong male, fights to the very end of his life and dies in battle.