^ I'm a human being, so I can only interpret a story from the point of view of a human being unless the subject's point of view is clarified. Since there's no explanation as to how this girl thinks or behaves, there isn't much to go on other than the reader's own interpretation. My personal interpretation is that the non-human aspects of her are simply symbolism, and not meant to be taken literally. The MC is afraid that this girl who seems to live completely without regard to normality will end up leaving her since she's incapable of that. It's very easy for positive-minded people to get trapped in a codependent relationship as an enabler, because they see the potential for good in people and think they can fix their abuser.
I think the main takeaway from this story is that there isn't a real sense of "bad end" or "good end," but lots of potential to go either way. It all depends on how willing the characters are to admit there is a problem.