Well, in certain fanfiction scenarios, Bella may have developed her own special powers or abilities that are not part of the original Twilight story. These could be used to defend the pack. For instance, she might have the power to create a protective shield around the pack's territory. Or she could have the ability to influence the minds of their enemies, making them turn away from attacking the pack. She might also be involved in diplomatic efforts, using her charm and intelligence to form alliances that would safeguard the pack.
In the original Twilight story, Bella has a main relationship with Edward and Jacob, and the idea of the whole pack imprinting on her is completely new. It deviates by adding a whole new level of complexity to Bella's relationships. Instead of just having the love triangle situation, she now has a connection with multiple members of the pack.
Obviously, Bella is one of the main characters. And then, the members of the wolf pack like Jacob are important. Jacob is often central as he has a complex relationship with Bella in the Twilight universe, and in the fanfiction, that relationship can be explored further in the context of the wolf pack.
One way is through her knowledge of vampire weaknesses. Since she has become a vampire herself in the series, she can share this knowledge with the pack. This knowledge can be used to create traps or defenses against vampire threats. For example, if a group of rogue vampires is targeting the pack, Bella can tell the pack about the vampires' aversion to sunlight and help them set up a situation where the vampires are exposed to it.
There could be a plot where Bella has a premonition about a danger that's going to befall the wolf pack. She then tries to convince them of the impending threat, but they are hesitant to believe her at first. Through her determination and the evidence she manages to gather, she eventually gets the pack to take her seriously and they all work together to face the danger.
Alice could dominate in Bella fanfiction through her strong personality. She is a very assertive character in the Twilight series. In fanfiction, she might use her charm and influence within the Cullen family to shape how Bella is integrated or treated. For instance, she could convince the family to keep certain secrets from Bella or expose her to vampire life more quickly than Bella might be ready for.
On the other hand, she could see it as an opportunity for a new start. She might gather her strength and decide to prove herself outside of the pack, or she could try to find a new group or community where she would be more accepted.
Bella might go into a deep depression. She was so in love with Edward, and his death could shatter her world. She could become withdrawn and isolate herself from her friends and family.
Edward would likely be in a state of panic. He loves Bella deeply, so he'd probably do everything in his power to save her. He might search for a cure or a way to reverse whatever is causing her to die.
I think Tanya would start by teaching Bella the importance of awareness in a fight. Then, she'd demonstrate actual fighting stances and combinations. Maybe she'd also have Bella practice against mock opponents to build confidence and skill.
In fanfiction, the idea of Bella having authority in the pack can be quite interesting. Fanfiction often takes existing characters and places them in new situations or gives them new traits. If Bella has authority in the pack, it could change the dynamics of the pack entirely. She might be in charge of certain tasks like organizing patrols or resolving internal disputes. Her authority could also bring new challenges as some pack members might resent her power, while others might look up to her. This concept can open up a whole new world of storylines and character development within the fanfiction.