Alice is another popular character. Her ability to see the future can be really interesting when combined with Bella's intelligence. For instance, Bella could use Alice's visions to plan ahead and make more intelligent decisions. Also, Jacob might be included, especially if the fanfiction involves Bella using her intelligence to solve problems between the vampires and the werewolves.
Obviously, Bella herself is a central character. Edward also remains important as he is her love interest. Their relationship as two vampires has a different flavor compared to when Bella was human. Also, Alice is often featured prominently as she can see the future and might foresee new challenges or opportunities for Bella as a vampire.
Bella herself is of course a very popular character. She is often the central figure around which the story revolves. Then there are the mobsters, like the powerful and brooding mob boss. His character is usually portrayed as having a tough exterior but a soft spot for Bella.
Well, obviously Bella herself is a central character. Jacob is also very popular as he is a werewolf in the original story and often has a complex relationship with Bella in the fanfiction. Then there are the other members of the wolf pack like Sam and Seth. They can play important roles in Bella's new werewolf life, either as mentors or as friends who help her adapt to her new identity.
Tinga Bella herself is of course extremely popular. She is the central figure and often the focus of most fanfictions. Her sidekick, if she has one, like a small magical creature that helps her, can also be a popular character. Another popular character could be her mentor, an older and wiser being who has taught her most of what she knows.
In Bella True Mate fanfiction, Bella is central. Her true mate is of course a key character, and he could be a werewolf alpha, a very popular choice as it adds an element of leadership and power to the relationship. Leah is sometimes included, especially if the story has a lot to do with the werewolf pack. There are also fanfictions where an ancient vampire, who has been hidden for centuries, turns out to be Bella's true mate. And the Volturi might make an appearance in some stories, either as a threat or an unexpected ally in Bella's relationship with her true mate.
Edward is still very popular. Since he and Bella are now both vampires, their relationship takes on new aspects that fans like to explore. Another popular character is Alice. Her ability to see the future could be really interesting in a story where Bella is a vampire. She could foresee events that involve Bella and help her avoid danger or make important decisions.
Bella is obviously one of the most popular. Since she is the main character in the original series, in fanfiction she often remains the central focus. Her relationships with the Cullens, especially Edward, are often explored in great depth.
I think Carlisle also has a certain popularity in Renesmee, Bella and Edward fanfiction. As the head of the Cullen family, his wisdom and his way of leading the family are often explored. And his relationship with Edward and how he influences Renesmee's upbringing can be a focus in some stories. Esme, too, can be popular as she represents the motherly figure in the family.
The daughter's friends in the fanfiction can be popular too. They could be other hybrids or supernatural beings that she meets during her adventures. For example, there might be a vampire friend who teaches her about the vampire culture or a human friend who helps her understand the human side of her heritage. And of course, any antagonists, like a rogue vampire who wants to harm the daughter for some reason, can also be a popular character as they drive the conflict in the story.
Alice Cullen can be a very popular character. Since she can see the future, in a 'reborn as bella swan' scenario, her interactions with Bella could be really different. Maybe she tries to guide Bella in a new way based on her visions. Also, Carlisle Cullen is popular. His father - figure role towards Bella might be explored further in these fanfictions.