Metal Slinger by Rachel Schneider

Brynn has spent the better part of her life waiting for the chance to attend the annual market hosted by the Kenta, the very same people who exiled the Alaha to live a life over the sea. A rite of passage for all young guards, she’s not sure what to expect from it, but breaking a century- long peace treaty certainly isn’t on her map.
Neither is the encounter with an enemy soldier.
Returning home to Alaha, she’s confronted with the aftermath of the day’s events. The future is uncertain as the threat of hunger looms over the people. With rumors of a growing rebellion, Brynn and her closest friends promise to stick together.
When an unexpected visitor arrives, Brynn’s loyalty will be tested as she learns of a world of magic and treachery. Once her enemy, always her enemy, right? But the dark, knowing eyes of a stranger make her question everything…
…including her heart.