Plastic Girl by Jessica Maison
Eva has never been a typical teenager. She grew up in a climate apocalypse, her parents are dead, and the boy she once loved is probably trying to kill her. A few years ago, she discovered a new species born from plastic waste, and she and her world became even stranger.
She quickly found she could mold these creatures into other beings - first a butterfly, then a fish, a deer, a bear - and eventually, a sister, Iris. These sisters learn to be a family as they rebuild the bay's ecosystem one creature at a time.
Right as Eva starts to believe she might survive the apocalypse and possibly save her planet, she gets sick, and just like that, she's dying of the disease that killed almost every human on Earth. Just like that, she’s not so special anymore.
While Eva and Iris race to find a cure, dangerous boys from Eva’s past sneak onto their island, threatening to destroy everything the girls have built. With each choice that Eva makes, it becomes frightfully clear that her creations, Iris included, will either save humanity or end it.