Immortal Dark by Tigest Girma

It's a tale as old as time:

Bloodthirsty vampire

Innocent maiden.

Except this maiden, isn't so innocent.

This maiden is a murderer. 

Orphaned heiress Kidan Adane grew up far from the hidden society she was born into, where human bloodlines gain power through vampire companionship. When her sister June disappears, Kidan is convinced a vampire stole her - the very vampire bound to their family, the cruel yet captivating Susenyos Sagad. 

To find her sister, Kidan must infiltrate the elite Uxlay University and survive living with Susenyos, even as he does everything he can to drive her away. As Kidan uncovers the heart of the ruthless vampire underworld, she grows determined to bring Uxlay to its knees. But when her thirst for revenge collides with Susenyos' lust for blood, the pair become entangled in a game of seductive desires and murderous secrets.