In a way, both Tom Robinson and Mayella Ewell are both victims. Tom Robinson is guilty of no more than being a good neighbor, and feeling sorry for a white woman. In Maycomb, feeling sorry for a white woman was a capital offense.
“And so a quiet, respectable, humble Negro who had the unmitigated temerity to ‘feel sorry’ for a white woman has had to put his word against two white people’s. (ch 19)
Mayella was an innocent girl, but she did accuse Tom Robinson. As Atticus points out to the jury, Mayella behaved as a child. She just tried to push the responsibility for her actions onto others.
She has committed no crime, she has merely broken a rigid and time-honored code of our society, a code so severe that whoever breaks it is hounded from our midst as unfit to live with. (ch 21)
However, if I was going to choose who was more responsible, it is definitely Mayella. She is the one who cried rape.