By the time of the trial, you could make the argument that Mayella is old enough to take responsibility for her actions and recognize differences in ethical choices. To an extent, she does because she is conflicted with how to act. But she has been living in an abusive environment, raising the children on her own, never going to school, and therefore never receiving any influence outside of that home. So, to a large extent she is a product of her environment and should get some sympathy; more than most people in the town who did not have to grow up in such an intellectually stagnant and backward family. Once in the light of the trial, facing the entire town, she feels she must lie to avoid the wrath of her father and to avoid being outcast even more by a town that still has racist tendencies and would look down on her for attempting to seduce Tom. Ironically, the only person in the story who treats Mayella with any kind of compassion or respect, is Tom and he’s the only one she will hurt by protecting herself.
I definitely sympathize with Mayella, but it is hard for me to empathize with her because I’ve never been in that position. Empathy is the ability to co-experience what someone else is going through. However, I would say that you can infer that many people in the town empathized with her because they, like her, would be conflicted between doing the right thing and their residual traces of historical racism. So, someone in town who was friends with blacks and whites would surely empathize with her because they probably have faced ridicule from their white friends for befriending black citizens. Mayella also deserves or would provoke empathy from any character who comes from a broken or abusive home. Empathy is a specific kind of sympathy; communal co-experience. Sympathy can be given regardless of life experience. It is also communal but is general compassion for the suffering of any human being.