Island's end / Padma Venkatraman.

Enhanced descriptions from Syndetics:

From the acclaimed author of Climbing the Stairs comes a fascinating story set on a remote island untouched by time. Uido is ecstatic about becoming her tribe's spiritual leader, but her new position brings her older brother's jealousy and her best friend's mistrust. And looming above these troubles are the recent visits of strangers from the mainland who have little regard for nature or the spirits, and tempt the tribe members with gifts, making them curious about modern life. When Uido's little brother falls deathly ill, she must cross the ocean and seek their help. Having now seen so many new things, will Uido have the strength to believe in herself and the old ways? And will her people trust her to lead them to safety when a catastrophic tsunami threatens? Uido must overcome everyone's doubts, including her own, if she is to keep her people safe and preserve the spirituality that has defined them.

Drawing on firsthand experience from her travels to the Andaman Islands, Padma Venkatraman was inspired to write this story after meeting natives who survived the 2004 tsunami and have been able to preserve their unique way of life. Uido's transformation from a young girl to tribal leader will touch both your heart and mind.