Sphaerie

Energetic, mischievous Ova really does want to blend her thoughts and memories with the sentient bio-engineered habitat Sphaerie, the only home she's ever known. How could she want anything other than to become one with mycelial-neural network nestled in the barren Southwest Desert? She'll learn to be serene. She'll learn to drift like a saccharine fairy in a web of shining loveliness. All she needs is a symbiont like the other kids in Sphaerie. But Ova's guardian refuses, saying she is too young and should explore her options. But there are no other options, so when one of the older girls wants to give up her symbiont and return to her family, Ova schemes to take the symbiont for her own.
The plan works...sort of. Ova doesn't understand why she can't settle down and meld into the habitat like the other inhabitants. Until she rescues a dog, finds a rogue symbiont living with a desert fox and stumbles into an abandoned colony which makes her question the history she's always been told.