We all know the first line of a query is your "hook." I call the last line the "sinker." You want it to punch them in the face, in a nice, friendly kind of way that makes them unable to forget you after having read the 300 other queries in their inbox.
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Some call her heartless, some call her ruthless--but most call her the Triple Point: The girl made of bone, ice, and hate. Good hook!
Helia Quinn knows about retribution. As the seventeen-year-old leader of the largest Organization on the eastern seaboard, it’s her job to dole out punishment as she sees fit. And even though Organizations are seen as the Robin Hood-esque “good guys” of the mob scene, Helia pulls no punches when it comes to her job as One. Capital "O" One? What does this mean / stand for? If you need proof, look no further then six months ago when she executed Jackson, the boy she loved, after he revealed himself as a traitor and broke her heart in the process. Awkward transition here with the direct address to the reader with "you." I would rephrase.
The past has taken it’s toll on Helia, but now it’s colliding with her present: Jackson’s younger brother, Noah, has picked off (up?) right where his brother left off and is now feeding information to Helia’s greatest enemy. Who would that be? Stopping Noah means infiltrating the private school he calls home and posing as a transfer student. What Helia expects to be an easy task quickly turns into the hardest mission of her life as struggles with her guilt over Jackson’s death and her increasing feelings for his brother. Because Helia knows all too well that friendship--and love--has its price.
TRIPLE POINT is a YA contemporary novel, complete at 67,000 words. The story will appeal to fans of the Gallagher Girls series by Ally Carter and MIND GAMES by Kiersten White.
Overall you've done a great job here, but I feel like there's a reference with "greatest enemy" to a bigger plot picture that sets the stage for the friendship / growing love story, but the query itself only references that bigger plot in passing. I think there needs to be at least a nod to what that larger plot structure is, but overall this is well constructed. Get an explanation for that "greatest enemy" in there and I think you're ready to go.