While some critics suggest that Mayella could be a symbolic mockingbird because of her father's abuse of her, she possesses some striking differences from Tom Robinson, one of the novel's figurative mockingbirds. Tom is completely innocent of manipulation or any wrongdoing. In fact, his very goodness is what leads him to be in the wrong place at the wrong time. Mayella, while admittedly innocent in the situation with her father, intentionally lures Tom into the Ewell home (she even saves up money so that her siblings will be out of the house during her attempted flirtation). Even though Mayella did not premeditate the framing of Tom for rape--that seems to be an act of self-preservation on her part--she does continue with her false story even when treated respectfully by Atticus and even when she knows that a man's life is at stake.
For critics who view Boo Radley as another mockingbird, Mayella does share some similarities with him. Both made poor choices (Boo's pulling a teenage prank, and Mayella's attempted seduction of Tom) which led to life-changing consequences. Both are awkward socially and elicit a fair amount of sympathy from the reader, and both have been mistreated by their fathers. However, Boo is a better fit as a mockingbird because he harms no one yet endures the ridicule of many. In contrast, Mayella is partly responsible for a man's death.
I don't think she symbolize as a mockingbird, sure she is a victom because her father physically and sexually abuses her, but she still lied and made Tom Robinson end up in jail and died.
It's Tom Robinson who is the symbol of the mockingbird. He is nothing but kind and helpful to Mayella and he is crippled but still works.