Depending upon what calendar you use, Olwen is either ten (Isis years) or sixteen (Earth years.) She thinks and remembers in Isis years, however, so let’s go with that. Despite this very young age, she actually has a fairly important, responsible job: transmitting various reports from the planet she lives on back to Earth.
She does this not because she is qualified, exactly, but because everyone else on the planet is either dead, unable to speak in words, or a not-completely trusted AI. And because, for various reasons, she can. That ability—well, strangeness, really—is what makes her The Keeper of the Isis Light.