The Deep Link (The Ascendancy Trilogy) (Volume 1)

Taryn Harber knows humanity must someday join the rest of galactic society. But the xenophobic TMC prohibits all contact. 

When a resistance cell calls on her for a dangerous first-contact mission, Taryn leaps at the chance. 

But her dream of making a powerful ally against the TMC turns into a nightmare. Taryn finds herself mentally linked to the ruthless warlord Amharr, and all chances of peaceful contact are lost. 

As she fights to regain her freedom, the Link starts changing Taryn from within. She is transformed into a living weapon, something she cannot control by herself. Something even her own people would kill to possess. 

Soon, Taryn must fight for much more than her life, and Amharr, who had no regard for another's life before, has become her last hope.