Why does Korede help Ayoola cover up her crimes in the novel, My Sister the Serial Killer?

Ever since Korede’s childhood, she was told to help and protect her younger sister. So, when Ayoola began to secretly murder people years later, Korede felt obligated to help Ayoola cover up these crimes and keep them secret. She is never able to bring herself to expose Ayoola’s crimes, as she remains inextricably bound by her sense of familial obligation.