In "To Kill a Mockingbird" did Mayella actually kiss Tom, or did she just tempt him like Atticus proposed?

There is only one person who has been willing to tell the truth about this matter, and that is Tom Robinson himself.  So, we have to look to his testimony to find out exactly what happened.  In chapter 19, we get Tom's side of things.  He describes how Mayella had him come in, then asked him to get something off of the chiffarobe; he grabbed a chair, did so, and then Mayella grabbed him around the legs, then hugged him around the waist, and then, "she reached up an' kissed me 'side of th' face."  So, according to Tom Robinson, she did kiss him, on the side of the face.  She then attempted to tempt him into kissing her back, saying, "Kiss me back, nigger".  Tom wasn't having any of that and got out of there as fast as he could.  So yes, Mayella did actually kiss Tom (if you believe him over her, that is), AND attempted to get him to kiss her back, just as Atticus hinted.