Most readers view Lady Macbeth as the more conniving, malicious one of her marriage in the beginning of the play. She does appear to have virtually no conscience, claiming a little water clears her and Macbeth from the act of murdering Duncan. But, thanks to Shakespeare's theme of appearance versus reality throughout the play, we realize that Lady Macbeth is actually the one who experiences guilt, whereas Macbeth demonstrates himself to be the malicious one. Through several soliloquies, Lady Macbeth admits she wouldn't have been able to murder Duncan herself and that she hasn't found contentment since his murder. By Act Five scene one, she is sleepwalking and deeply disturbed by the blood she has waded into with Macbeth, who incidentally even keeps his actions regarding Banquo and Macduff from her, which is in large contrast to how he treated her in the beginning of the play.
If you're looking for quotes, I would look first to her soliloquies. They're short, but telling of her mental state.
Lady Macbeth is strong-willed in the beginning of the play. She decides as soon as she reads her husband's letter in Act 1, sc. 5, that Duncan must be killed. She hounds her husband until he agrees, in Act 1. sc. 7, to kill Duncan. She attacks his manhood, telling him that he won't be a man in her eyes if he doesn't do this deed. In reality, she does have a conscience, even though she tries to hide it. She even chastises her husband for showing sadness and regret after Macbeth kills Duncan in Act 2.
By Act 5, sc. 1, the guilt of all the deeds gets to her and she goes insane. While she sleepwalks in that scene, she laments over the murders that have been committed - that of Duncan, Banquo, and the Macduff household. Whether Macbeth ever told his wife or not about the murders of Banquo and the Macduffs is unclear, but she knows that her husband committed them. She is able to keep her head about her until after the murder of the Macduffs.
In Act 3, sc. 4, she is the one who tries to keep order when Macbeth sees the ghost of Banquo at the banquet and reacts, startling his guests who do not see the ghost. She goes from a strong woman to a mad woman.