In (1.5.45-60) Lady MacBeth is still very strong, very dominant, and very full of the vaulting ambition which will, by the end of the play, topple her marriage to MacBeth and cast the Crown of Scotland into a bloody struggle. In this first soliloquy Lady MacBeth calls on "spirits / that tend on mortal thoughts" to "unsex" her here, take her womanly "milk for gall" and fill her up with "direst cruelty." She is calling for arcane and demonic powers to take away what is good, kind, and nurturing in her nature so that she can be ready for the plans she has for her husband and for attaining the crown of Scotland through regicide.
In (5.1) she is a mere shadow of her former self. She is now psychologically damaged and her mind is like her husband's--"full of scorpions." In this Act, Lady MacBeth sleepwalks, talks in her sleep, and is curiously seen by the doctor and nurse to be washing her hands and murmuring, "out damned spot!" and "what, will these hands never be clean?" (5.1.37-45). As MacBeth was at a high station and "falls" so too does Lady MacBeth and the audience is privvy to this "fall." Lady MacBeth is now steps away from committing suicide and ending the psychological torment she's put herself in.