There are a few instances. One occurs in chapter 23 when Aunt Alexandra tries to explain to Scout why she can't befriend Walter Cunningham. Aunt Alexandra is showing her prejudice toward the poor, lower class citizens of Maycomb here. By explaining to Scout that the Finches are better than normal people, Aunt Alexandra is doing the exact opposite of what Atticus has fought so hard for throughout the book - to defend the innocent and do the right thing, regardless of race or class.
A second example occurs in the next chapter, when Alexandra has her elitist friends over for lunch. They are discussing how much better life is in Maycomb as opposed to other, heathen parts of the world (never mind that an innocent man was just found guilty of rape). Mrs. Merriweather talks about how fortunate Scout is to live in a Christian home while a missionary has to venture out into foreign lands full of sin and squalor. This should bring to mind Ms. Maudie's quote about how the Bible in some people's hands is worse than a bottle. Mrs. Merriweather is unable to see her own sin and corruption evident throughout Maycomb.
A third example is when Scout's teacher is talking about the atrocities the Nazis are doing to the Jews. This strikes Scout as odd because she saw the teacher calling for Tom Johnson's head at the trial. How could she feel bad for the Jews yet hate Tom? Simple: she is racist.