Lady Macbeth is presented as outwardly fair and kind, but inwardly as an evil, manipulative woman. She is determined to carry through the witches prophecies to her husband so that he becomes King, and she Queen.
In Act I, scene v, Lady Macbeth is concerned that her husband may take some convincing in order to carry out her desires. She demands him to "Hie thee hither/ and let me pour my spirits in thin ear" and convince him to adopt her plan. She even asks the spirits of evil to help her become evil enought to carry out the plan herself if need be:
Later, upon seeing that Macbeth is vascillating in his decision, she has to use vivid imagery to convince him. She calls him a coward that has broken his promise to her and vows that
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, had I so sworn as you
Have done to this. (I,vii).
Her willingness to kill a child if she had promised is powerful and does sway Macbeth's choices, showing Lady Macbeth to be evil and manipulative underneath a pretty and sweet exterior.