Edited with an (even further) updated version:
After waking up decades before her cryostasis was supposed to end, seventeen-year-old Amy must stop a murderer from killing the other frozens trapped on the space ship before her parents are unplugged.
I am absolutely not opposed to rewriting again, so feel free to rip this sentence up, too! :)
Ironically enough, your comments have also inspired me to entirely rewrite my query letter too! I am going to create, essentially, two pitch sentences (one for each POV character, as this story switches between them), and use that as a launching point for the query summary. Even if I don't end up placing in the pitch contest with this sentence, I'm thrilled that I now have a stronger query just because of the help you all have given me this weekend!
Thank you ALL so much for your help!