What is Cassie and real reason for acting like a servant for Lillian Jean In the book roll of thunder hear my cry?

Cassie acts like a servant for Lillian Jean to avoid a conflict that would put her and her family in danger, as well as to protect her pride and self-respect in a segregated society where black people are expected to defer to whites. This act of subservience is a survival strategy for Cassie to navigate the racial dynamics of their community.