>>90709209I can think of management problems easily being the main reason.
It wouldn't surprise me if management prioritizes idol/music activities when they try to resolve problems. Fauna doesn't mind the idol activities, but doesn't do more than expected, so anytime she has problems or has new ideas/projects she doesn't get priority compared to the rest of the girls who do.
This could easily mean that any of her grievances never get resolved, and the problems keep piling up. She sees the difference in treatment and she doesn't feel like cover is giving her enough support to stay so she simply leaves.
This means all sides are not lying and simply saying the truth. The same thing could've happened to Ame too, her random ideas might've been left in the back burner because they don't get priority. So she gets fed up and decides to leave to do everything by herself.
At the end of the day it's still a problem that should be resolved, either by giving their personal managers more freedom to decide things which I don't expect to happen with a Japanese company, or by hiring more staff to make sure every single girl has her problems resolved which imo is a terrible idea that will just increase management bloat.