In Chapter Nine, why does Bri feel she has to split her Sundays at church between sitting with Jay and sitting with her grandmother?

In Chapter Nine, Bri feels she has to split her Sundays at church between sitting with Jay and sitting with her grandmother because her grandmother likes Bri to demonstrate in front of the congregation that she still feels loyal to her. Bri lived with her grandparents for some years while her mother was recovering from addiction.