Lauren Haywood is an optimistic worrier. [Meaning what? She's optimistic that none of the horrible things she worries about will actually happen?] Ever since she saw monsters barging into her house and her parents being mauled in the blink of an eye, [she's become a pessimistic worrier. Can you blame her?] she took [has taken] it upon herself to find food so that the same thing wouldn’t happen to Dustin, her brother, [If she finds food, monsters won't maul her brother? Why not?] even with the beratement she received. [What was she berated for, and by whom?] So that they could live to reach an evacuation centre. [Which is a place you go when you've evacuated another place?]
But in the middle of their traverse, a mountain lion disrupted their path and turned on them. [It's pretty standard to use present tense when summarizing a plot.] Dustin barely surviving with lethal cuts, and then ambushed by Unawakened, she exerted herself beyond the limits to save themselves. [Terrible sentence. Easier to delete it than to try salvaging it.] When she manages to come [comes] to, a stranger is with her and with some hesitation, they accepted his help to guide them to the nearest evacuation [centre]. [That sentence starts in present tense and ends in past.]
After Dustin and Lauren were successfully admitted, everything went back to an almost daily-like life. [I assume a daily-like life is a life that passes one day at a time. But what is an almost daily-like life?] Just with some exception of fighting and learning how to combat and protect, while blending in as a human, [Are they human?] courtesy of her parents’ instruction. When Dustin was conscripted into the patrol, some residents took advantage of his absence and threatened Lauren. For the price of revealing her elemental power in self-defense, she was thrown into jail to be executed.
Storming [Brainstorming?] for ways to escape, Cory, the stranger, told her her brother wasn’t one of the three survivors from the patrol. Lauren broke herself out with assist [help] from Cory and went to find him. Discovering him with a three-day-old bite mark, Cory explained that he knew someone who could help. A biologist. Unknowingly, she stepped into the trap. He disclosed that her father, James Haywood, was an instigator of wars between Mages and humans. That Cory’s father was killed by him. That he anticipated the day he could have his revenge.
Kept and experimented [Imprisoned and tortured,] she tried to escape and succeeded [escaped], but [was] caught when she searched for Dustin. Tied in front of the residents, the crowd riled up [This says that the crowd is tied in front of the residents. Also, people can get riled up or rile up other people, but they don't just rile up. ] at the notion of the instigator’s daughter at their mercy. [Seems more likely they'd be thirsting for blood than getting riled up.]
Day after day passed agonizingly by when [until] help came in the form of a boy. As they broke out with a kidnapped Cory, they headed to their destination to rescue Dustin : Twin Falls. The place where their parents died.
There's no point to working on a query and synopsis until you improve your writing skills by doing lots of reading and writing and studying, paying special attention to word meanings and grammar. Sorry to sound so evil, but when you submit to Evil Editor, you know what to expect.