According to feminism theory, despite her show of strength, Lady Macbeth’s eventual weakness is a result of the portrayal of her gender.
Portraying women as weak.

Society encourages Lady Macbeth to invest herself in being a mother. Lady Macbeth is seen as selfish and needless to say weird, when she confesses that there is a situation in which she would “ Dash her childrens' brains out" (I.vii). A very unsettling statement, according to societies belief that women’s desire to have and protect their children is a part of their very being. Which contradicts what lady MacBeth proclaimed

Although she is intelligent and strong at the beginning of Macbeth, Lady Macbeth is reduced to an insignificant person that is haunted by nightmares and guilt as a result of the portrayal of her gender.

Lady MacBeth and Feminism