Apex by Mercedes Lackey

Being a member of the Elite Hunter Command imperils Joy in more ways than one. In their latest clash with Othersiders, the army of monsters nearly wiped them out. Apex City is safe, for now. But within the city barriers, Joy must wage a different kind of war.
The corrupt and powerful PsiCorps is determined to usurp the Hunters as chief defenders of Apex City and Joy is now squarely in their crosshairs. Unused to playing political games, she has very few people she can truly trust-not even Josh, her first friend in Apex City, who broke up with her when it became too dangerous for a Psimon to be dating a Hunter.
Then Josh comes to Joy for help. He fears that Abigail Drift, the head of PsiCorps, will soon use him in her twisted experiments designed to empower PsiCorps and render Hunters superfluous--a scheme that's already killed off dozens of Psimons. Joy manages to smuggle Josh to safety, but he cannot evade Drift forever?
As Joy faces ever more powerful Othersiders, she is helped by the most surprising ally imaginable--the same Folk Mage she once met in battle on the train to Apex City. But can Joy trust the most cunning and treacherous of all Othersiders?
In the thrilling finale to Mercedes Lackey's #1 New York Times bestselling trilogy, Joy must risk everything to end a brutal war, before she loses all she's ever loved.

This book is part of the "Hunter" series.
Here are some other books from this series: