Summary from Goodreads:
Daughter of immortals.
Princess Diana longs to prove herself to her legendary warrior sisters. But when the opportunity finally comes, she throws away her chance at glory and breaks Amazon law—risking exile—to save a mortal. Diana will soon learn that she has rescued no ordinary girl, and that with this single brave act, she may have doomed the world.
Daughter of death.
Alia Keralis just wanted to escape her overprotective brother with a semester at sea. She doesn’t know she is being hunted by people who think her very existence could spark a world war. When a bomb detonates aboard her ship, Alia is rescued by a mysterious girl of extraordinary strength and forced to confront a horrible truth: Alia is a Warbringer—a direct descendant of the infamous Helen of Troy, fated to bring about an age of bloodshed and misery.
Two girls will face an army of enemies—mortal and divine—determined to either destroy or possess the Warbringer. Tested beyond the bounds of their abilities, Diana and Alia must find a way to unleash hidden strengths and forge an unlikely alliance. Because if they have any hope of saving both their worlds, they will have to stand side by side against the tide of war.