Answer:
It is unclear whether Lula speaks for the majority opinion in the congregation. While she is vocal about her opinions, the text does not provide enough information to determine whether others in the congregation share her views or not.
The author may have included Lula in the church scene to provide a contrasting perspective to Calpurnia's, who had previously expressed her desire to bring Tom's wife Helen to church. Lula's reaction to the children's presence in the church highlights the racial tensions and divisions within the community, which is a central theme of the novel. Additionally, Lula's outburst serves to further emphasize the importance of Calpurnia's decision to bring Jem and Scout to church and to expose them to the realities of racial inequality.