Why does Mayella feel that Atticus is mocking her in 'To Kill a Mockingbird'?

Because Atticus treats her with respect by calling her "Mrs.Mayella" and Ma'am
Because he is just addressing her politely,but she doesnt go to school.so she dosent know how to address people.
Mayella thinks that Atticus is making fun of her, because he was simply being courteous and polite. Growing up in the harsh Ewell household, she had never received any respect. Therefore, she thought that Atticus was being sarcastic and was mocking her.
No one has ever called her Ms. Miss. or Ma'am before in her life.

When Atticus calls her this at the trial, she seems to think that he is mocking her.
Mayella is not used to being shown respect. When Atticus calls her ma'am or miss, she thinks he is mocking her.