Jia Ling had indeed dyed her hair purple. In a program, Jia Ling showed her lively and humorous personality, but she was not used to the way she dyed her hair. In addition, Jia Ling also mentioned in the box office goal of the movie Hello, Lee Huanying that if the box office reached 2 billion, she would dye her hair. However, there was no more specific information about Jia Ling's hair dyeing.
If it's a hair tie given to her by a friend, it could strengthen their bond. For instance, if it was from Angela, it would be a symbol of their friendship. Whenever Bella looks at it, she's reminded of their good times together, and it might make her more likely to reach out to Angela when she's having a problem, thus deepening their relationship.
In this fanfic, Sakura coloring her hair might be part of a self - discovery journey related to Sasuke. She might start with her natural hair color, feeling a bit ordinary in Sasuke's perception. So she takes the bold step of coloring it, perhaps a bright pink which is more vibrant and shows her new - found confidence in her love for him. This change in her appearance could lead to various interactions with Sasuke, from his initial surprise to a possible deeper connection as he starts to see her in a new light.
It might change her relationship with Ron. He could be initially shocked but then grow to like the new look, seeing it as a sign of Hermione's independence. Or it could cause some tension if he preferred her old look.
A girl at the waterpark with her hair in a bun could be the start of a really interesting fanfiction. She could be a shy girl who usually keeps to herself. But at the waterpark, something changes. She sees a group of people playing a really fun water game and decides to join in. As she plays, her bun starts to come loose, which adds a bit of humor to the story. And through this experience, she gains more confidence and makes new friends.