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.
The Prophet's Daughter is a set in a post-apocalyptic world suffering from the consequences of orchestrated murder - an attempt at genocide. Sixteen years after the initial destruction and spread of the disease that ravaged the human race, Arin is thrown headfirst into the world without any skills of her own to keep her alive. OK - lots of questions arise here. If there's an attempt at genocide, who specifically was targeted? I assume this is set on Earth, so the question of genocide means you will be saying who was being murdered by whom, which has the possibility of raising sticky questions, at best. Also, is the disease the weapon? Or is this something else that followed on the heels of the human genocide? And why would Arin have no skills to survive? You say that she is "thrown headfirst into the world," so where was she for the 16 years before that? The book follows her journey as she begins to discover the truth of how the world became what it has become and learn the true reason for her parent’s murder.
This is a pretty short query, which is good because you have plenty of space to expand and answer all the questions above. As it stands right now this query is too vague - there are tons of already published post-apocs and I'm sure many more hopefuls on the desks of agents and editors. Get the details of what makes yours different and unique into the query.