What are some quotes in the book To Kill a Mockingbird I can use that would support that Mayella is a perpetrator?
Two quotes I can use to say that Mayella is a bad person out to hurt an innocent man only because he's black.
Atticus certainly believes that Mayella is lying when she claims that Tom beat and raped her, and he spells out her reasons plainly in his summation to the jury (in Chapter 20). According to Tom's testimony, Mayella asked him to come into the Ewell house and, once inside, she kissed him and hugged him. He said that she told him it was planned in advance, since she had saved nickels for a whole year so she could send the other Ewell kids to buy ice cream. She told Tom that since she'd never been kissed before,
"... she might as well kiss a nigger. She says what her papa do to her don't count. She says, 'Kiss me back, nigger.' I say Miss Mayella lemme outta here..."
An important point here is her statement that what "papa do to her don't count," which suggests an underlying possibility that an incestuous relationship was going on between Mayella and Bob. Since Bob probably beat her afterward, this would also help to explain why they chose to blame Tom to cover up Bob's own attack.
In his summation, Atticus declared that
"She knew full well the enormity of her offense... she tried to put the evidence of her offense away from her... she struck out at her victim... She must destroy the evidence of her offense.
"She was white, and she tempted a Negro. She did something that in our society is unspeakable: She kissed a black man."