Plastic Girl

Eradication is the final book of the Plastic Girl trilogy.
After a mysterious research ship filled with dangerous newcomers arrives, Eva and Iris fight to maintain the fragile alliance between the polylilakes and humans. In the exhilarating conclusion of the Plastic Girl series, the two species must come together or suffer total eradication.
Plastic Girl is a YA climate sci-fi trilogy with a companion prequel novella.
Eva grew up in a climate apocalypse, her parents are dead, and the boy she once loved might be trying to kill her. Just when she's about to give up hope, she discovers a new species born from plastic waste. More incredibly, she can mold the creatures into other beings-first a butterfly, then a fish, a deer, and eventually a sister, Iris.
As the sisters unlock a power that can save the planet, dangerous teens discover their island, threatening to destroy the new life they've created. The species born from plastic can reverse the climate apocalypse, but it may wipe out humanity in the process. In the spirit of Lord of the Flies, the two species will either come together and live in paradise or kill each other in a wasteland. One sister will leave the other behind, testing the ties of their found family as another more symbiotic way forward is revealed, one more terrifying than extinction.
"Maison has crafted an enigmatic, surreal SF castaway tale that ultimately pays off with a suspenseful account of a fight for survival." (Kirkus Reviews)
"Eva's mysterious world is developed in a fantastical but thorough manner that makes it immersive. Its atmosphere is immediate and affecting, with tie-ins to the present that show what pollution and climate change, if unchallenged, could result in. Harsh realities are confronted throughout in a logical and involving way... In the fascinating world of the young adult novel Plastic Girl, teenagers confront the realities of climate change. It's a compelling cautionary tale. (Foreword Reviews)