The Gordian Knot: Schooled in Magic, Book 13

The post of Head Girl of Whitehall looks fantastic on anyone's resume. It places the lucky winner on equal terms to the staff, granting them authority, power, and responsibility that no other student can even dream of possessing. A student lucky enough to win the coveted post is destined for greatness. Everyone will want to know their name.

Naturally, Emily doesn't want it. 

But when she returns to Whitehall for her sixth and final year, she discovers that the staff has elected her to the post - and refusal isn't an option. Worse, the Grandmaster wants her to run his pet project - a formal dueling club - even though it's the last thing she wants to do. Reluctantly, she starts to carry out her new duties, unaware that deadly enemies are waiting in the shadows, preparing themselves to strike at her when her back is turned. Someone is spreading rumors about her, someone is sabotaging her projects, someone is weakening the ties that bind her to Whitehall.

And, as matters start to spin out of control, as the life and soul of one of her closest friends is thrown into terrifying danger, Emily must decide between carrying out her duties or walking away, knowing that either choice will cost her dearly...and leave her alone at the center of a deadly storm.