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.
Lady Macbeth is ambitious and, may be, even wicked, but she is definitely ambitious and wicked with a difference. In her second soliloquy in act1 sc.5, she apostrophises to the powers of darkness and evil in order to be cruel enough so that she can stand by the side of her husband in fulfilling his ambition for the throne. In act 1 sc.6, when King Duncan arrives at Inverness, Lady Macbeth plays the role of the hostess with all the studied and affected idiom of hospitality. In act1 sc.7, when the unsettled Macbeth tells her--'We will proceed no further in this business', she remonstrates him with all indignation and sarcasm. She goes to the extent of showing her cruelty in a strained violence of language:'I have given suck, and know/How tender 'tis to love the babe that milks me:/I would, while it was smiling in my face,/Have pluck'd my nipple from his boneless gums,/And dash'd the brains out....'
But in the scene of Duncan's murder, we find Lady Macbeth in visible nervous tension, very apprehensive and appalled by the noises of the night. She is apprehensive whether Macbeth can make the heinous attempt; she is appalled by the owl's cry. She has taken a dose of wine to make her strong, and yet she feels unnerved. She claims that 'Had he not resembled/My father as he slept, I had done 't'. But the conditional claim is doubtful because a woman/mother who could have killed her own child in the most gruesome manner should have killed Duncan all by herself. In act 2 sc.3, Lady Macbeth faints and she is carried out. That seems to be the first manifestation of her mental degenaration ultimately leading to sleep-walking and suicidal death.
Lady Macbeth is very much a woman whose selfless ambition to see her husband on the throne motivates her to invoke the powers of darkness. She invites a moral backlash of remorse and guilt which is manifest in her words of regret in act3 sc.2:'Nought's had, all's spent./Where our desire is got without content:/'Tis safer to be that whichwe destroy/Than by destruction dwell in doubtful joy'. In the scene of her sleep-walking, we find a an agonised woman constantly rubbing her hands to remove the imaginary stain and smell of blood. She mutters her sufferings, her doubts, fears, desperation and anguish. No throughly wicked person would have gone through such a mental hell. She dies soon thereafter; dies a pathetic suicidal death.