How does Cassie reveal her lack of sophistication on the day she goes to Strawberry in Roll of Thunder, Hear My Cry?

Cassie was expecting Strawberry to be a big, sprawling
town, but she was highly disappointed when she got her first glimpse at it. "Is this
it?" Cassie cried. A paved road and electric lines were the only modern conveniences she
could see. She then became upset when she saw other vendors with better locations to
sell their goods. Big Ma warned her to watch her mouth and to stay put whlle she visited
Mr. Jamison. But Stacey took off and Cassie followed. Inside the Barnett Mercantile
Store, Cassie became upset when several white people received preferential treatment,
and Cassie protested. She lost her temper and argued with Mr. Barnett, who called her
a "little nigger." When Stacey returned, Mr. Barnett ordered them both out of the store,
but not before Cassie screamed at the owner once
again.

Cassie's youthful ignorance did not allow her to
understand the place of the Negro in the white man's world. She did not know her place.
It was perfectly normal at that time for white customers to be waited upon before
Negroes, and patience and humility were not virtues that she yet
possessed.