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.
If you're looking for query advice, but are slightly intimidated by my claws, blade, or just my rolling googly-eyes, check out the query critique boards over at AgentQueryConnect. This is where I got my start, with advice from people smarter than me. Don't be afraid to ask for help with the most critical first step of your writing journey - the query. My comments appear in green.
In 1928 Vermont, rebellious Amelie Lecuyer thinks her (try "a" instead of "her" to avoid the echo) clandestine romance with her womanizing, alcoholic boyfriend Jonathan is her biggest worry at seventeen. Hmm... the age coming in last isn't the best sentence construction, I'd fit it in elsewhere. It isn't until her Abenaki this should probably be explained as I don't know what Abenaki is and I'm guessing the agent wouldn't either ancestry comes to light and her brother is murdered because of racial bigotry that she discovers her family lineage is a far more dangerous secret
When her brother's killer, the governor's ruthless son Revelin, begins to target her how do you begin to target someone? Just "targets" is fine, she is left with little choice but to flee to her distant and long forgotten tribe
Amelie is persuaded by her tribe to train as a Brave, but quickly finds she is not cut out for this violent, insufferable calling. Consequently, when she is presented with the sacred spring that brings the depths of one's soul to light—turning iniquitous people into Tsinoo and purifying the Braves to give them the ability to defeat them—her struggle with inadequacy collapses into fear. What if she turns into a Tsinoo?
Recklessly defying her tribe, she runs away and regrettably incites incalculable consequences where she must decide where her loyalty lies—with her tribe or with Jonathan. Jonathan comes back into the picture way late here.
Overall the actual structure and writing here is fine, but more explanation in terms of content is needed. What is an Abenaki, specifically? You explain Tsinoo and that they have paranormal qualities but not what an Abenaki is or does. The job of a Brave is described but I don't know what it actually is or what is required that makes it "insufferable." What are these "incalculable consequences" that you refer to? It's a very vague statement to use when referring to a plot point.
Also, Jonathan is mentioned first, last, and nowhere in between. How does he fit into the middle of the story? Why would her loyalty to the tribe interfere with her loyalty to Jonathan? Also we need to know more about our MC - she's categorized as "rebellious" but then is suffering from feelings of inadequacy. Not necessity mutual exclusive traits, but why the change?
THE HEART OF A BRAVE is a stand-alone novel with series potential, complete at 84,000 words. YA Historical Fantasy.