Five at the start of the novel, little Ruth May doesn't get to be much older. We have to keep dodging the anvil of foreshadowing, too, since our narrators keep telling us things like she "tears through her life like she plans on living out the whole thing before she hits twenty" (2.4.6). But, really, there's so much of it that you can basically close your eyes and point to a random page; you'll probably find some hint of her death.
Ruth May's too young to analyze her surroundings and the things she's going through. She can simply tell us about them, with the honesty only a five-year-old (and Rachel) has, and then leaves it to us to figure it out. And one thing we figure out is that Ruth May, like all the other daughters, has a major case of daddy issues. Ruth May feels guilty constantly, which we see when she worries endlessly about skeevy Eeben Axelroot's smuggled diamonds. He tells her that if she tells anyone, God will make her parents get sick and die—and we have to wonder if Ruth May would have swallowed this lie so wholeheartedly if her own father hadn't already instilled in her a needless fear of the good Lord.
Another thing she gets from her father is the need for "something to boss around" (3.5.1). She easily wrangles up the children into a game of Mother May I?—too bad her father isn't taking lessons from her. He might have been able to figure out how to communicate with the people of Kilanga.
Ruth May makes the childish mistake of hiding her quinine pills and getting malaria. Oops. (But that's not even what kills her.) At first, it's hard to tell if what she's seeing is real, or a fever-induced hallucination. One thing that's definitely for real is the thing that seems most like fantasy, namely the nkisi given to her by Nelson. It's to save her from dying by making her disappear and reappear in a safe place.
Okay, sure, it doesn't quite work the way Ruth May expects, but it does work. Check it out: when the snake bites Ruth May, Leah says, "Just for the moment it was as if she'd disappeared, and her voice was thrown into the trees" (4.9.2). And it stays there. The very last chapter of the novel is unlabeled, but we're pretty sure it's told by Ruth May, whose spirit is hanging out in the trees, able to see all, past, present, and future.
Perhaps it all ties into the Congolese belief in muntu: "There is no special difference between living people, dead people, children not yet born, and gods—these are all muntu" (3.2.3). In death, Ruth May doesn't cease to exist, she just exists differently—and in the end, she's just another daughter who the Congo won't let go.