Final answer:
Ruth May's final message to her mother in The Poisonwood Bible is her declaration that she wants the family to be reunited and for her mother to come back home with them.
Step-by-step explanation:
In the novel The Poisonwood Bible, Ruth May's final message to her mother is not explicitly stated. However, the last interaction between Ruth May and her mother occurs when her mother tries to give her money and Ruth May resists taking it, saying, "I'm not taking any money to go away with. I'm coming back with all of us together." This can be seen as Ruth May expressing her desire for the family to be reunited and for her mother to come back home with them.