Battlefield

Possibly. 

If she made it out of the Battlefield alive with her Unit composed of eight people just like her, she's promised the freedom she had only previously dreamed of. But in order to do so, she must kill members of other rival Units fighting for the same thing.

When you're raised to be a weapon, fighting - killing - is the only thing you know. At least, that's what Gerard, her breeding partner, constantly tells her. 

​​​​​​​Just because they were, quite literally, made for each other didn't mean they had to like each other, but they definitely had to trust each other if they wanted to survive.