Royal Magic by K.M. Shea

Gwendafyn is slowly suffocating.

As the second princess of the elves of Lessa she is the acting regent of her people and is expected to behave with the serene grace and poise of a model elf. But that is not who she is. Instead, her very character is constantly criticized as being too passionate, too fiery, and overall “too much”.
The former Crown Prince of the human country of Calnor, Benjimir’s disinheritance has permanently altered his future and place in court. It gets worse. He is forced to watch as the woman he has secretly loved his whole life narrows down her marriage prospects. He may ordinarily revel in his own ruthlessness, but this feels like his heart is dying.

Gwendafyn is given a chance to flee the role that has ensnared her when she realizes there is one escape that not even her family traditions can prevent: marriage to a human from Calnor.
With most humans and elves unable to speak the same language, her options are limited. She starts to lose hope when the human translators only see her title and treat her with fear and awe.
Yet there is one other human who can speak the language of the elves: the scorned Prince Benjimir.
But Gwendafyn isn’t that desperate.

At least not yet.
It starts as a marriage of convenience and an opportunity to strengthen the bond between their two peoples. But what if it could become something more?