Because of how the story was told (it can be quite disjointing at times), it didn't feel to me like there were actually two persons -- namely, Beverly and Elliot.
It seems to me more like it's the story about this one person, Beverly, who suffers from split personality disorder (dissociative identity disorder). Beverly is withdrawn, and constantly struggles with her inner self, even when she was in her altered self of her sister, Elliot. Although Elliot died when she they were young, she continues to live on in Beverly's mind.
Subconsciously, Beverly wanted to move on with her life, but discovered in time that it was impossible. Her love and attachment to her sister was far too strong. She felt that Elliot deserved a chance at her happiness too, and so ultimately made the decision to make her altered self the dominant self.
It seems to me more like it's the story about this one person, Beverly, who suffers from split personality disorder (dissociative identity disorder). Beverly is withdrawn, and constantly struggles with her inner self, even when she was in her altered self of her sister, Elliot. Although Elliot died when she they were young, she continues to live on in Beverly's mind.
Subconsciously, Beverly wanted to move on with her life, but discovered in time that it was impossible. Her love and attachment to her sister was far too strong. She felt that Elliot deserved a chance at her happiness too, and so ultimately made the decision to make her altered self the dominant self.