If Lady Macbeth was controlling and had little to no humanity, why did she kill herself? Was she manipulating Macbeth into doing the wrong things because she was obsessed with being queen?

Lady Macbeth is most certainly as ambitious as her husband, and she manipulates him into assassinating King Duncan. After receiving news of the seemingly favorable prophecies, Lady Macbeth fantasizes about becoming queen, questions her husband's resolve to become king, and calls upon evil spirits to consume her body in order to make her callous, hostile, and malicious. She proceeds to ensure her husband that they will get away with the murder, and she plans the entire assassination. Whenever Macbeth expresses second thoughts about committing regicide, Lady Macbeth harshly criticizes him and challenges his manhood. Clearly, she is ambitious to become queen, and she even participates in the assassination by placing the daggers back into King Duncan's chamber.
Despite Lady Macbeth's initial resolve and callous nature, she becomes overwhelmed with guilt following the assassination. She begins to sleepwalk and hallucinates about washing Duncan's blood from her hands. Eventually, Lady Macbeth's conscience gets the best of her and she cannot overcome her guilt, which motivates her to commit suicide. Her overwhelming guilt indicates that she does possess humanity and have a conscience. Similar to her husband, Lady Macbeth's ambition leads to her demise.