I am number 20

Number 20 came to earth with 24 other children when she was 5 years old to escape the dark force counsel. Since then 16 children have died. She is now 16 years old. There is another alien race called the drk force councel . They destroyed their own home planet and want to destroy the planet Gia. They did so and are out to destroy the children an destroy earth.number 20 has to survive and save earth. But how much longer can she do it?

Sorry for the crappy description. This is my first time for this stuff so bear with me!