Shattered Warrior

It is eight years after Colleen Cavanaugh's home world was invaded by the Derichets, a tyrannical alien race bent on exploiting the planet's mineral resources.
Most of her family died in the war, and she now lives alone in the city. Aside from her acquaintances at the factory where she toils for the Derichets, Colleen makes a single friend in Jann, a member of the violent group of rebels known as the Chromatti. One day Colleen receives shocking news: her niece Lucy is alive and in need of her help. Together, Colleen, Jann, and Lucy create their own tenuous family.
But Colleen must decide if it's worth risking all of their survival to join a growing underground revolution against the Derichets ... in Sharon Shinn and Molly Knox Ostertag's Shattered Warrior.