That her father, Mr. Ewell, had abused her, not Tom Robinson.
Atticus wanted the jury to have a picture of Mayella's life because he was trying to get everyone to see that she has to do all the chores, and she like the "outcast" of the family. He was also trying to show that Bob Ewell gets mad and drunk a lot at Mayella. And that is how she gets beat, and raped.
In To Kill a Mockingbird, the similarity between Atticus and Bob is that they both didn't want their children to suffer, when Atticus heard that Bob was dead he was worried that Jem, his son had killed him and he was concerned about the implications that would follow. The same with Bob, he was attempting to save his child, Mayella, from the shameful act she had committed with a black man (Tom Robinson) and wanted him put away to avoid shame to himself, his family and her.
Atticus doesn't seem upset, but rather happy that Bob Ewell challenged him. Atticus said that it was better that Mr. Ewell took out his anger on Atticus. If not he would take out his anger on one of his children, which Atticus didn't want.
The fact is that Mayella's injuries were mainly on the right side of her face, meaning whoever beat her was left handed (basing there hits with there left hand) Mayella's father is left handed, but Tom Robinson could barely use his left hand, making Atticus prove that it was Bob (but hey, you know the ending)
Atticus asks Mr. Bob Ewell to write his name on a piece of paper while he is cross examining him. Mr. Ewell writes his name with his left hand, so he is left handed, which proves that Tom Robinson could not have raped and beaten Ms. Mayella Ewell, because Tom Robinson's left arm is completely crippled from an accident he had long ago. Ms. Mayella Ewell had been beaten on the right side of her body. Atticus shows that it was Bob Ewell who beat Mayella, but due to the racism in Maycomb, Tom Robinson was wrongly convicted as a black man.
He wanted revenge on Atticus and was low enough to go for his kids.
To form a lynch mob, to show that they don't like Tom and want him dead for allegedly raping Mayella Ewell
Jem does not want Scout to tell Atticus about Bob Ewell's comment because he fears that it might upset Atticus and cause trouble. However, it is not wise to keep such important information from Atticus, as he is their father and can handle the situation appropriately. It is important to communicate openly and honestly with trusted adults when dealing with serious matters.
Mr. Ewell likely didn't call a doctor after Mayella was attacked because he didn't want the authorities involved due to the illegal nature of the situation. Additionally, seeking medical help would have drawn attention to the abuse and potentially implicated him as the attacker.
She claimed that she called him in her house to chop up an old dresser that her father didn't want anymore.
In "To Kill a Mockingbird," Bob Ewell attacked Jem and Scout Finch behind the school after the pageant in retaliation for their father Atticus Finch humiliating him in court. Bob Ewell sought revenge on the Finch children because he felt that Atticus had made a fool of him during the trial, and he wanted to hurt them as a form of payback.
Atticus thinks Boo Radley killed Bob Ewell to protect Scout and Jem. He does not want the truth covered up because he believes in justice and honesty, and wants the events to be revealed in court for a fair resolution.