Question: At the end, who was part of the travelling circus that Mattie didn't like?
Answer: Rooster Cogburn. She considered him a legendary lawman, like Wyatt Earp. She felt bad that he was reduced to being a sideshow attraction in a circus.
Question: After Rooster carries the snake-bitten Mattie back to the cabin and fires shots to alert the people inside, he collapses. What does he say then, was it, "I've grown old?"
Answer: Yes. He groans, "I've grown old."
Answer: It was Frank James, brother of Jesse. He didn't stand up as she approached. She was offended by his lack of manners.