Books in the Subterrene War series

Catherine is a soldier. Fast, strong, lethal, she is the ultimate in military technology. Bred by scientists, indoctrinated by the government, she and her sisters will win this war, no matter the cost. And the costs are high. The life span of these genetic soldiers is short, and they become unstable as they age. Then on their eighteenth birthday, when their duty is fulfilled, they are discharged - lined up and shot.But the truth is, Catherine and her sisters may not be strictly human, but they aren't animals either. Catherine may have only known death, but she dreams of life - and is prepared to pay any price to get it.