In to kill a mocking bird, what according to Atticus is the thing that Mayella has done wrong?

That she is blaming an innocent man by claiming that he has sexually assulted her (raped) even though she had slept with that innocent man (Tom) she is trying to get herself out of her own problem that she had created in the first place. Her crime, as Atticus says in Chapter 20, is that she "was white, and she tempted (flirted with) a Negro."