How does the social, the economic and the familial prejudice in To Kill A Mockingbird lead to conflict?
The arrival of Aunt Alexandra in Maycomb causes the greatest conflicts in the Finch household. Alexandra believes that the Finch family stands head and shoulders above all others in the town, and her beliefs in "gentle breeding" and "fine folks" are difficult for Scout to understand. While Scout is able to differentiate between the honest but poor country folks like the Cunninghams and the poor white trash Ewell family, Alexandra sees no difference between the two families. She believes that, like the Ewells,Walter Cunningham Jr. " 'is--trash' " simply because his family is poor and not a part of Maycomb society. Alexandra wins this battle, since Walter Jr. is never allowed to come and play with Scout. Nor does Alexandra consider Calpurnia a part of the Finch family, believing that Cal is no longer necessary once Alexandra asserts her place as the female head of the Finch family. Alexandra is not comfortable with the power that Cal wields in the household, and Atticus's sister is hardly as racially sensitive as her brother. Luckily for his children, Atticus puts his foot down when Alexandra demands that Cal be fired, reminding his sister that
"... she's never indulged them the way most colored nurses do." (Chapter 14)
As mentioned in the above answer before mine, in the great American novel To Kill a Mockingbird, we get good insight into the Finch family. In your question, you are asking to examine the social, economical and family prejudices within the Finch household that leads to conflict. As seen above, the characters of Scout and Alexandria have conflicting views of a more lower class family. Scout is able to understand and sympathize with the lower class and poorer families, however, Alexandria is not. She just sees them as trash and puts those families at fault.
Unfortunately, in the world we live in today, it is very difficult to rise and get out of poverty. As seen in this specific situation, although Alexandria says the other poorer families are trash, she is too naive to realize that it is not really their fault. It's the system they are born into.
Many examples such as this one are portrayed throughout the book. They look at these situations through the economical and family prejudice perspective that you have mentioned in your question.