Based entirely upon Mayella's testimony, she hates everyone--Tom, Atticus, Judge Taylor and the jury. She has no doubt been coached (although minimally and poorly) by her father, and she seems hesitant to be present in such a public situation. It can be assumed that Bob beat his own daughter, and then accused Tom to cover up his own actions. He had no choice but to force Mayella to go along with his own story. Unfortunately for Mayella, her story had many holes in it, and Atticus was quick to point them out. Mayella appears to be scared to death during her entire testimony, including during the friendly questioning by the prosecutor, Horace Gilmer. She begins crying at his first question, and Judge Taylor has to constantly remind her that she's "a big girl" and has nothing to fear. Scout sees the hatred in Mayella's eyes as she leaves the witness stand:
I never saw anybody glare at anyone with the hatred Mayella showed when she left the stand and walked by Atticus's table.
Her outburst toward everyone in the courtroom made her feelings clear.
"... if you fine, fancy gentleman don't wanta do nothin' about it then you're all yellow, stinkin' cowards, the lot of you..."
Mayella must have at one time appreciated Tom's helpful nature, if you can believe Tom's own testimony. She hugged and kissed Tom, telling him that since she'd never kissed a man before, and that she "might as well kiss a nigger." But her own testimony refutes Tom's statement, and she claims that Tom beat her and "done what he was after." The fact that Mayella was perfectly willing to allow Tom to face execution shows that she cared little for him and had no remorse for her own actions.