Edenfall. Genesis Earth Trilogy, #2

The ultimate truth requires you to sacrifice your innocence. Sixteen years ago, Estee's parents abandoned their scientific mission to the planet Icaria and made the new world their home. They thought it would be decades before anyone else came to this rugged, edenic paradise. They were wrong.   Young, fearless, and free, the only other people Estee has ever known are her own immediate family. So when a military expedition arrives from Earth, she is innocently drawn to all the interesting new people, their large, noisy vehicles, and their strange weapons.
  But her parents have a secret. There is a dark side to Estee's homeworld, whose distant past is linked to Earth's terrifying future. Now Estee is the guardian of those secrets, and she must do all in her power to keep them from falling into the wrong hands. As the marines begin to hunt her, Estee makes an unlikely friend in a young lieutenant. Together, they must unlock the secrets of Icaria's past to break the cycle of violence and restore their shattered worlds.