The Rat Queen

The human race is losing the battle for freedom to move within the galaxy - or even to survive as a species, if some galactic nations have their way. A feral toddler growing up among rats in the air vents of a space station could be the key to the future of humanity.
The story follows a family of orphans who adopts the little girl who thinks she's a rat, along with their adoptive father, who had escaped from his home planet just before it was destroyed.
The space station is operated by galactic beings hostile towards humanity. To them, rats and humans are equally vermine. However, they allow all the humans they had imprisoned there to go to resettle a vacant planet. But there was a reason why that planet was abandoned by the previous human population.
The little girl who thinks she's a rat is a key to their survival.