She might be more assertive. Since she is related to Klaus, she may inherit some of his confidence. So instead of being the meek Bella we know from the original, she could be more outspoken and take charge of situations.
The original Bella was mainly focused on her relationships with Edward and Jacob. But in this fanfiction as Klaus's sister, she would be more involved in the supernatural politics. Her character development would be shaped by the power struggles and alliances in the vampire - werewolf - witch world that Klaus is part of. She might start to see the world in a more strategic way, thinking about how to protect her family (including Klaus) and gain power for them. For example, she could be learning how to manipulate other supernatural beings to their advantage, which is a far cry from the Bella who was just trying to survive high school and deal with her love life in the original story.
In the original, Bella is more of a damsel in distress. But as an assassin in fanfiction, she becomes more independent and self - reliant. She no longer waits for others to save her but takes matters into her own hands.
Since Bella is already a vampire, her character development could focus more on her coming to terms with her new existence in a different way. She might not have the same initial struggles with bloodlust as she does in the books. Instead, she could be more interested in exploring the vampire culture and history right away. This would lead her to interact with different vampires, not just the Cullens, and gain a broader understanding of their world. This, in turn, would shape her character into a more worldly and independent vampire.
Bella's character might become more confident. Knowing she has a powerful brother like Aro could give her a sense of security. She may also become more assertive in vampire society.
She might become more protective. As Silas's sister, she would have a natural inclination to safeguard him, which could make her more assertive.
Bella's character development in this fanfiction might be seen in her emotional growth. Initially, she might be a bit naive and overly curious about the Cullens. But as she grows up with them, she becomes more understanding and empathetic towards their situation. She may also learn to control her emotions better, especially when it comes to the dangerous aspects of the vampire world. For instance, instead of panicking all the time, she starts to think rationally and find solutions. Moreover, her relationships with the Cullens shape her into a more complex and well - rounded character. Her bond with Edward might deepen in new ways, and her friendships with the other Cullens could also influence her values and behavior.
She could also develop more compassion. Knowing she's bringing a new life into the world, she might start to see things from a different perspective, especially when it comes to the relationships within the Cullen family and their views on her pregnancy. This could lead to her trying to bridge gaps and bring the family closer together.
In some fanfictions, Bella's character might become more confident. As an immortal, she no longer has the same fears of mortality. For example, she could be more fearless in facing dangerous situations.
Bella's character often becomes more confident. As a vampire, she has newfound strength and abilities that make her less timid. For example, she may be more assertive in her relationships and in dealing with threats.
Bella could develop a stronger sense of survival. In the face of the mob's threat, she has to constantly be on the lookout for danger. This would make her more aware of her surroundings and better at finding ways to stay alive. For instance, she might learn how to hide, find safe places to stay, and avoid being detected. As she overcomes various challenges during her escape, she may also gain more confidence in her abilities. Initially, she might be very scared and unsure, but as she manages to evade the mob's pursuit, she realizes that she is capable of much more than she thought.
Bella's character might become more confident. Without Edward, she has to rely on herself, which forces her to grow. As a vampire, she'll be more physically capable, and this could translate into mental strength as well.