Reign (The Reign Duology #1) by RI Aryn:
 
When Fate nocks her arrow, no one can stop it from striking. A battle between the feye and the elves, a race against time. There can only be one winner—until a secret is unveiled.

When Nyra Daville feels the last of her depleting powers wither away, she is left a powerless queen in the face of her subjects. The threat of the three empires of the feye realm’s downfall forces the allying Crowns to pursue a quest in search for the enchanted stones that hold their magic.

A journey of trust and betrayal, truths and untruths.

Nyra can’t risk losing control of herself with all that is at stake. Not at the risk of rekindling forgotten feelings.

Not when Zyran Varadi is back in her life.

It’s a twisted and dangerous game they play, one that risks the undoing of both their kingdoms. And they may very well have ruined it all in the process of protecting the feye.

Forbidden and deadly, everything she never should have allowed to happen.

At the end of it all, one question will Nyra be able to prove, to herself if no one else, that she is worthy of her title as queen?