A Kingdom of Destruction by Ivory K. Rose

Two kingdoms at war.
Brutal fae magic.
One girl could be the key to ending it all.

When the youngest human princess, Aven Elridge, turns the tides of the war between humans and fae with her fierce legions and her father’s brilliant plan to use their own form of magic against the fae, everyone believes the humans have all but won.
That is, until the fae take revenge too far, slaughtering Aven’s siblings and forcing her to cross the borderlands as their prisoner to keep the human king in line.
As the fae try to convince her to stop the war by marrying one of the princes, she resists with her iron will, believing it is only another trick. But both Crown Prince Cillian, with his kindness and pretty words, and his brother Roran, with his dark swagger and thinly veiled innuendos, make it harder to ignore what’s in front of her.

With grim news from her kingdom, Aven is forced to make a choice to save her remaining human subjects and the life of her father.
One she’s terrified she’ll live to regret.