Think for a moment. Who was her daughter? Did she ever exist? Her Whismur is named after her. Unless Whismur is actually her daughter caught in Bill's experiment. Anyways,Zinnia suffers a mental health disorder thinking someone important to them existed,yet the viewer never sees them in person. Stories about a nonexistent person changes all the time and can change the person's behavior and personality. Think for a moment why she is wild and suddenly calm in some scenes. Aster nevet existed, she was just some form of hallucination Zinnia thought real. Then Zinnia was told to move on and leave Aster behind meaning her daughter doesn't exist and only you can change your heart and accept reality.