Lady Macbeth begins rejecting the femininity of her gender when she demands that she be unsexed. There seems to be a visible mid-way transition in what she rejects when Macbeth declines to disclose his plans for Banquo to her: "Be innocent of the knowledge, dearest chuck,/ Till thou applaud the deed." In the end, it seems the only thing Lady Macbeth rejects is her actions when she laments that there is neither enough water nor perfume in Arabia to cleanse the blood and smell from her hands.
After reading Macbeth's letter—which he closes by saying that he doesn't want her to be "ignorant of what greatness is promised thee [her]"—she begins the process of rejecting her feminine qualities by contemplating the need to chastise Macbeth and to pour the "valour" of her words into his—the warrior's—ears. By saying this, she identifies herself with masculine traits relating to war, killing, and ambition. As her ambition heats up for the attainment of Macbeth's kingship and her own queenship, Lady Macbeth goes further and further in rejecting feminine characteristics by demanding that the spirits "unsex me here, / And fill me. . . top-full / Of direst cruelty!" and that they come to "my woman's breasts, / And take my milk for gall."
It can be argued that in the midst of Macbeth's torment over the role Banquo might play, Lady Macbeth begins a transition away from vehement rejection of feminine qualities. This is evident when she laments the unfolding outcome of events: "Nought's had, all's spent." Immediately after this reflection, Macbeth enters. Instead of pouring valor and venom into Macbeth's ears, she consoles him, calling upon the feminine trait of comfort-giving to do so: "Things without all remedy / Should be without regard: what's done is done."
Shortly after that, we see Lady Macbeth be secretly observed by a doctor attempting to diagnosis her strange behavior. Macbeth has already seen Banquo's ghost at the banquet. Lady Macbeth has already tried to rouse him and accused him of being "quite unmann'd in folly." Now she is walking in her sleep, pantomiming washing her hands "this a quarter of an hour"—an ironic turn of events, as she earlier told Macbeth that a little water would wash Duncan's blood from his hands—and she is longing for the perfume of Arabia to get rid of the scent of blood from her hands. Here we see a Lady Macbeth who now rejects her past actions that her mind is unhinged.