Molly of Mars in Pirra's World: Alien Cages

Slowly, Molly, Vicky, and Pirra are adjusting to life on Sephia Prime. They are homeless, scared, and on the run. Molly's hate for the warriors is intensifying but her fears keep her from progressing. She wants to rescue the girls in the impenetrable prison in the Capitol. However, she reminds herself often that rescuing herself and her friends is the easier choice. She made the easy choice in the past.

For ages 10+.

All the books in the Molly of Mars series:

Molly of Mars and the Alien Syndicate
Molly of Mars and the Alien Nebula
Molly of Mars and her Alien Sister
Molly of Mars and the Alien Creatures
Molly of Mars in Pirra's World: Alien Spacegates
Molly of Mars in Pirra's World: Alien Cages
Molly of Mars in Pirra's World: Alien Revolt

Or try my other teen+ series, Lunara.