Some fanfictions may feature the black hair tie as a sign of a secret society within the Twilight realm. The character with the hair tie on their wrist is a member, and they have to keep it hidden from the other factions. The story could revolve around the secrets they keep and the danger they face if discovered.
A popular one is 'Hair Tie, New Beginnings'. This fanfiction focuses on how the simple hair tie on Bella's wrist becomes a way for her to communicate her feelings to Edward without words. For example, she might tighten it when she's nervous around him or loosen it when she feels more at ease. It's a really cute and unique take on their relationship.
Another idea is that the hair tie on the wrist is a symbol of a secret relationship. In the Twilight world, where relationships are often complex and secretive, a character could wear the hair tie as a sign of their connection to another. It could be a way for two characters to communicate their feelings without words, like a secret code.
Perhaps in the fanfiction, the black hair tie on Jade's wrist is a clue to her past. She has amnesia and the hair tie is the only thing she has from her previous life. As she begins to investigate, she meets various characters who either try to help or hinder her in uncovering the secrets associated with the hair tie.
In some fanfictions, the hair tie is described in great detail. Writers might focus on its texture, like if it's made of silk or something more rustic. This can add to the overall atmosphere of the story. If it's a silky hair tie, it could give a sense of elegance and refinement, while a more rustic one could suggest a connection to a simpler or more earthy part of Bella's life.
Another possibility is that it's related to the overall theme of the fanfiction. If the story has a lot of dark or mysterious elements, the black hair tie could be a small detail that ties into that. It might be a clue for readers, something that will be revealed later in the story to have a greater significance, like being part of a magical or supernatural object.
A fanfiction could revolve around a mom with a black hair tie on her wrist who is a superhero in disguise. The hair tie is actually a magical object that gives her powers when she ties her hair back. She has to keep it a secret from her family while still saving the day in the neighborhood.
The black hair tie on Rachel's wrist might be a symbol in a fanfiction. It could represent her connection to a secret society. Only those who notice the hair tie are part of the group, and throughout the story, Rachel has to keep it hidden from those who would oppose the society.
In hair fanfiction, a black hair tie on the wrist can symbolize a connection to a particular character. It might be something that the character left behind or a memento. For example, if it was from a love interest, it could represent an unspoken bond or a longing for that person.
Perhaps the hair tie has some kind of magical or special property in the fanfiction. It could be that it was once part of an ancient ritual, and Emily unknowingly wearing it on her wrist has put her in a position of power or danger. The story could revolve around her discovering the true nature of the hair tie and how it affects her relationships with the other characters in the Twilight universe, such as Leah and the rest of the pack.
I'm not sure of a specific one off - hand, but you could try searching on fanfiction - specific websites like Archive of Our Own. There might be some hidden gems there that center around this unique concept of a twilight black hair tie on the wrist.