Shrouded Sky — Tracy A. Akers

A teenage girl bound by ancestral memory. Two enemies determined to claim her. A phantom island veiled by time. A relic that could destroy two worlds. And it's all real. Seventeen-year-old Chandra thinks sailing with her father is dull punishment -- until she's shipwrecked on an island thought to be only fiction. But when she learns an antiquity once owned by her treasure hunting father was actually a protective device stolen from the island, she becomes trapped in a conspiracy that could reach far beyond its shores. Unbeknownst to Chandra, she harbors ancestral memory which makes her both enemy and ally to two warring factions. But it is her knowledge of the relic's last location that is the real threat. When two opposing warriors fight to claim Chandra for their cause, she discovers it is not only her knowledge they desire, it is also her heart. Unfortunately, both will require a sacrifice: all of her memories must be erased, including her loyalty to those she now calls friends.