Perhaps it represents a connection to a past event. For example, she wore it during an important moment and now it's a reminder. In a fanfiction set in a post - apocalyptic world, it could be a memento from before the disaster.
The hair tie could be a connection to her past. Maybe it was from a special event or person. For example, it could be from a school event where she had a great time with friends. In the cave, it gives her a sense of normalcy and comfort in a strange environment.
In fanfiction, a girl with a dirty hair tie on her wrist could be a sign of her being in a hurry or perhaps she's been through some sort of adventure. Maybe she was so caught up in an event that she didn't have time to clean up or change her hair tie. It could also be a unique characteristic given to her by the author to make her stand out. For example, in a fantasy fanfiction, it might be a charm that has some special power but just looks like a dirty hair tie.
It could be a symbol of love. For example, her secret admirer gave it to her, and she wears it to keep that person close to her heart, even if she doesn't know who they are yet.
It could be a simple fashion statement. Abby is known for her unique style, and the hair tie on her wrist might just be another part of that.
The hair tie might be related to a prophecy. In the fanfiction's lore, there could be a prophecy that mentions a girl with a black hair tie on her wrist who will save the world. Felicity, unknowingly, is that girl and as the story progresses, she discovers her true destiny.
Maybe it's a memento. In fanfiction, it could be from a special event or person. For example, perhaps it was given to her by Rory during one of their study - filled nights. It represents their friendship and all the shared experiences they've had while pouring over books and notes.
In fanfiction, the hair tie on the wrist could symbolize the trainer's connection to a certain Pokemon. For example, if they have a Pokemon that likes to play with the hair tie, it shows a bond between them. It could also be a sign of the trainer's preparedness. They are always ready for any situation, whether it's to keep their hair out of their face or to use the hair tie for some other creative purpose in their adventures.
The hair tie could be a memento from a loved one. Maybe it was her mother's hair tie before, and wearing it makes her feel close to her mom even when she's in the pool having fun.
In fanfiction, a black hair tie on the wrist could symbolize a connection to a particular character. Maybe it was given by a love interest, and the character wears it as a reminder of that person. It could also be a sign of a secret society or group within the fanfiction world, where the black hair tie is a form of identification.
The hair tie on the girl's wrist in the rain could be a symbol of a past relationship. Maybe it was given to her by an ex - boyfriend, and as she stands in the rain, she is reminiscing about the good times they had. Every time the raindrop touches it, it brings back a memory.