Edward could be an interesting character to pair with her. If Bella is a non - human, their relationship would take on a whole new dynamic. For example, if she's a mermaid, Edward, as a vampire, would have to deal with the differences in their species. Another good character could be Jacob. If Bella is some kind of supernatural being, Jacob's wolf nature could create a complex relationship with her, full of loyalty and conflict.
Rosalie could be paired with Bella. Suppose Bella is a phoenix. Rosalie, with her strong personality, would have a unique reaction to Bella's powers of rebirth. Their relationship could start off rocky but develop into a strong friendship or more. Also, Esme could be a good pairing. If Bella is a faerie, Esme's nurturing nature could help Bella adapt to the human world she's living in, while also learning about Bella's faerie ways.
Jacob could also make a great pairing. He has his own relationship with Bella, and his werewolf nature could create a lot of drama when interacting with the vampire sister. They might start off as enemies but gradually find common ground, like their shared love for Bella in a way, and then develop a deeper relationship.
Edward is often still a key character. If Bella is not human, their relationship dynamic would change drastically. For example, if Bella is a vampire, they might have different power levels or views on being a vampire, which could create conflict or a new kind of bond. Another character could be Jacob. If Bella is some sort of magical being, Jacob's werewolf nature might interact with her in unexpected ways, like an alliance or a rivalry.
One idea could be that Bella is a vampire hunter who was turned into a vampire against her will. Now she has to navigate the vampire world while still holding onto her human values. Another could be that she's an alien disguised as a human named Bella, and she's on a mission to study Earth's culture. Maybe she falls in love with a human and has to decide whether to reveal her true identity.
The author could be anyone really. It could be a fan who was tired of seeing Bella in a more passive role and decided to create their own version where she isn't a wimp. It could be from a person within the fan community who has a passion for re - imagining characters in different ways.
Her best friend could be the first one to help. They might notice the signs of malnourishment like her pale skin and lack of energy. They start by sharing their lunches with her at school.
Her partner could be a main character. He would play an important role in how Bella copes with the situation. They could have deep conversations about their future together and support each other through the emotional turmoil.
A doctor named Dr. Smith could be a main character. He could be a strict but fair physician who at first doubts Bella's abilities but later comes to respect her.
Jacob could also be a popular character. If Bella is not human, his loyalty and friendship towards her might be tested in new ways. He could be either accepting of her new form or struggle with the changes in their relationship.
Caroline Forbes could be a great addition. In 'The Vampire Diaries', Caroline is a strong and sassy vampire. In a fanfiction with Damon, Bella, and her, she could be a source of both conflict and support. She might be jealous of Bella's relationship with Damon at first, but then end up being an ally, especially if there's a common enemy.
Alice could be a great addition. She could be Bella's best friend who is always trying to play matchmaker between Bella and Jasper. She has this uncanny ability to sense when things are going well or not so well between them and gives her two cents whether they want it or not.