What evidence from the text helps you to infer that Lady Macbeth feels guilty about her role in the murders?

Most of the evidence to support the idea that Lady Macbeth feels guilty about her role in the murders comes from Act 5, scene 1: the sleepwalking scene.  First, Lady Macbeth seems to be hallucinating, believing that there is still blood on her hands, as there was on the night she returned the daggers to Duncan's bedroom and smeared his chamberlains with blood.  Now, in her sleep, she says, 

Out, damned spot, out, I say!  [....] Yet who would have thought the old man to have had so much blood in him?  (5.1.37-42)

It sounds as though she's referring to King Duncan, and she fears that she cannot wash Duncan's blood off of her hands.  This is ironic because it was she who told Macbeth, immediately after the murder, "A little water clears us of this deed" (2.2.86).  Now, however, she feels that "All the perfumes of Arabia will not sweeten this little hand," and she cries piteously (5.1.53-54).  This certainly makes her seem remorseful and guilty. 
Another one of the crimes more recently committed by Macbeth is the murder of Lady Macduff and her innocent children, a crime he ordered out of anger with the poor woman's husband.  Lady Macbeth essentially planned the murder of Duncan and goaded Macbeth into doing it, but, since then, Macbeth has planned several additional murders, including those of children, all on his own.  She now seems to feel some guilt for creating this monster when she says, "The Thane of Fife had a wife.  Where is she now?  What, will these hands ne'er be clean?" (5.1.43-44).  It was she who pushed Macbeth to perform the first murder, and then he proceeded to become crueler and more violent, losing any sense of guilt he once possessed.  Her question about Lady Macduff seems to imply that she feels at least partially responsible for her role in these later murders too.