Aunt Alexandra's opinion of the trial is not stated in the book, however, she did mention she didn't approve of it (however, she didn't state her opinion on whether Tom Robinson is innocent or guilty), yet she was hurt when she saw the way the people of Maycomb treated Atticus. The way she kept her opinion to herself is representative of her will to censor her opinion for the well-being of Atticus and the children. Hope this helps! :)
