What does Mayella think of Atticus?

If you are referring to Atticus' questioning of Mayella in court, Mayella thinks that Atticus is purposely being condescending. She thinks he is making fun of her. Mayella is also afraid that Atticus' questions will confuse her in the same way they confused her father, directly referring to Atticus' revelation that Mr. Ewell was left-handed.

What are you scared of?”

Mayella said something behind her hands.

“What was that?” asked the judge.

“Him,” she sobbed, pointing at Atticus.

“Mr. Finch?”

She nodded vigorously, saying, “Don’t want him doin‘ me like he done Papa, tryin’ to make him out lefthanded…”