She might be portrayed as a villain by showing her being manipulative. For example, she could use her relationship with other characters to get what she wants, like using Edward's love for her to control his actions or decisions.
Well, in some fanfictions, she might be depicted as the devil through her actions. Maybe she's shown as being manipulative, using her charm to get what she wants from others, much like how the devil is often portrayed as a tempter in traditional stories.
In this fanfiction, Bella Swan as Hecate could be depicted as a very wise and mysterious figure. She may use her knowledge and powers to protect those around her. Just like Hecate is often associated with crossroads, Bella might be in a position to make important decisions for the characters in the story. She could also have the power to transform things or people, which is a characteristic often linked to Hecate.
Perhaps there was a time - warp incident. She got stuck in a time - loop or something similar that caused her to experience 2000 years while the outside world moved at a normal pace. This would create an interesting dynamic in the story, as she might be the only one aware of the true passage of time, and she would have to deal with the consequences of her long existence, like the loneliness and the burden of her many memories.
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.
To develop Bella in this fanfiction, she could be given a mentor. Maybe an old witch who has been watching over her. With the mentor's help, she can learn about the history of doppelgangers in the witch world and how to control her powers. She can also struggle with the morality of using her powers, like whether she should use them to get revenge on those who have wronged her in the past.
She might become more assertive. As the daughter of Ares, she would inherit some of his war - like traits. So, instead of being the somewhat passive Bella in the original story, she could be more proactive in making decisions and taking action. For example, she may no longer wait for others to protect her but instead take the lead in dangerous situations.
Well, perhaps she could show Artemis' independence. Artemis is known for being self - sufficient and Bella might be depicted as not relying on others much in the fanfiction. For example, she could be shown as a great hunter like Artemis, using her skills to fend for herself and protect those she cares about.
In the fanfiction, Bella Swan as a fallen archangel may be seen as a more rebellious character. Her fall from grace could be seen as an act of defiance against the rules of the celestial realm. This new aspect of her character could lead to a whole new set of adventures and challenges, different from the love - triangle - centered plot of the original 'Twilight' series. She might be more focused on finding her place in the new world she has entered rather than just on her relationships with Edward and Jacob.