How does Atticus say he feels about Mayella Ewell?

In Chapter 20, Atticus gives his summation at the end of the trial. He says that he pities Mayella, but does not condone the lies she has told about Tom: 

I have nothing but pity in my heart for the chief witness for the state, but my pity does not extend so far as to her putting a man’s life at stake, which she has done in an effort to get rid of her own...

In Chapter 20, Atticus gives his summation at the end of the trial. He says that he pities Mayella, but does not condone the lies she has told about Tom: 

I have nothing but pity in my heart for the chief witness for the state, but my pity does not extend so far as to her putting a man’s life at stake, which she has done in an effort to get rid of her own guilt. 

Atticus goes on to discuss the "code" that Mayella broke. She, a white girl, attempted to seduce a black man. This went against the racist code of the south in the 1930s, the time in which this novel is set. Mayella, feeling embarrassed and guilty for breaking this code, chose to incriminate Tom instead of telling the truth about what she did. Atticus recognizes the guilt she felt, but he says it doesn't justify putting Tom's life in jeopardy. Atticus also blames the society itself for allowing such a code to continue to exist.

In the end, even though Mayella and Bob conspired to ruin Tom, Atticus still has pity for Mayella. She is the victim of a poor, ignorant father who mentally and physically abuses her. In Chapter 23, we learn that Bob Ewell has spit in Atticus' face. When Jem asks him if he's worried about more retaliation from Bob, Atticus explains how his refusal to fight back is based upon sympathy for Mayella:

Jem, see if you can stand in Bob Ewell’s shoes a minute. I destroyed his last shred of credibility at that trial, if he had any to begin with. The man had to have some kind of comeback, his kind always does. So if spitting in my face and threatening me saved Mayella Ewell one extra beating, that’s something I’ll gladly take. He had to take it out on somebody and I’d rather it be me than that houseful of children out there.