Another possible main character could be a rival. Someone who is jealous of Bella's flying ability and tries to undermine her. This creates conflict and drama in the fanfiction.
The main characters are clearly Gaara and Sakura. Gaara, the once - lonely and misunderstood shinobi from Sunagakure, with his unique sand abilities. And Sakura, the intelligent and strong - willed kunoichi from Konohagakure, known for her medical ninjutsu and her growth as a fighter.
I'm not entirely sure as the story isn't widely known to me in a very specific sense. But generally, there would likely be the people who can fly. Maybe there are leaders among them who guide the others in using their flying ability.
As I said before, if it's about the Wright brothers' story, then Orville and Wilbur Wright are the main characters. They were the ones who worked hard to make the first powered flight possible.
There could be a female character, Sofia, who is another member of the mafia. She sees Bella as a threat at first, thinking she'll steal her position or the attention of the men in the mafia. But as time goes on, they might form an unlikely alliance. There may also be a young and ambitious mafia underling named Antonio, who is always looking for ways to climb the ranks and his actions often impact Bella's situation in the story.
The main character is always Bella in this type of fanfiction. However, new characters could be introduced as well. For instance, a blind mentor who has learned to live fully with blindness could be added. This character could guide Bella and help her accept her condition. Or there could be a villain who tries to take advantage of Bella's blindness, which would then lead to a conflict where Bella has to use her wits and other strengths to overcome the villain.
There could be Edward. Even if Bella is now immortal, Edward might still play a significant role. He could be either her eternal love or her adversary depending on how the fanfiction is written. Another character could be Alice. Since Alice has her own special abilities, she might be there to help Bella navigate the new world of immortality. For example, she could foresee some of the challenges that Bella will face. Also, Jacob might be a main character. His relationship with Bella, whether it's a friendship or something more complicated, could be further explored in the context of Bella's immortality.
There could be Edward. Maybe he is involved in Bella's life with her psychic powers. He might be curious about her abilities or even try to protect her from the consequences of using those powers.
Since we have no details about the 'fly girl novel', the main characters could be a group of friends that the fly girl has. They could be involved in all kinds of escapades together. Or it could be that there's an antagonist, someone who tries to stop the fly girl from achieving her goals, and this antagonist would also be a main character in terms of driving the plot forward.
There could be a protagonist who is preoccupied with the fly. This character could be someone going through a period of boredom or self - reflection. The fly then becomes an object of their attention, and through their interaction with it, we learn about their character traits, like whether they are cruel, indifferent, or empathetic.
I don't know as I haven't read it. But they could be a group of young women with unique personalities.