Swarm by Rhea V. May

A merciless villain. A woman who has tasted the sour tang of betrayal. And a mistake—that against all odds, reunites them.

With solid virtues and a lack of pretense, Melissa Mason has never wished for impossible things. Even blessed with above-average intelligence, she has never sought to surpass her Tert status.
But then she meets him—Oron A’Keni, the Emperor of the Kessar. And everything changes.
Before, she believed in his lies. Now, she lives and breathes fury. He called her his most precious, then stabbed her in the back.
Before, she thought him a victim. Broken and misguided. Now, she sees the truth.
Before, she dreamed about their bright, love-filled future. Now, she pictures the alien bastard’s face when her blow will come.
Hiding from everyone and everything, Melissa couldn’t care less about the crisis Earth is facing, with the threat of extinction a hair’s breadth away. All she wants is revenge.
And nothing is going to stop her. Not even the latest development, where she finds herself joining him on a trip—into the past.
But to survive this unknown universe, she has to postpone her greatest wish and form a reluctant team with the only person capable of keeping her safe.
All too soon, Melissa realizes her fears were unfounded. For there’s no greater danger than falling back in love with the arrogant emperor.A merciless villain. A woman who has tasted the sour tang of betrayal. And a mistake—that against all odds, reunites them.

With solid virtues and a lack of pretense, Melissa Mason has never wished for impossible things. Even blessed with above-average intelligence, she has never sought to surpass her Tert status.
But then she meets him—Oron A’Keni, the Emperor of the Kessar. And everything changes.
Before, she believed in his lies. Now, she lives and breathes fury. He called her his most precious, then stabbed her in the back.
Before, she thought him a victim. Broken and misguided. Now, she sees the truth.
Before, she dreamed about their bright, love-filled future. Now, she pictures the alien bastard’s face when her blow will come.
Hiding from everyone and everything, Melissa couldn’t care less about the crisis Earth is facing, with the threat of extinction a hair’s breadth away. All she wants is revenge.
And nothing is going to stop her. Not even the latest development, where she finds herself joining him on a trip—into the past.
But to survive this unknown universe, she has to postpone her greatest wish and form a reluctant team with the only person capable of keeping her safe.
All too soon, Melissa realizes her fears were unfounded. For there’s no greater danger than falling back in love with the arrogant emperor.