Maybe in the fanfiction, Bella wears Edward's clothes as a statement. It could be a way for her to show that she belongs to him in a sense, or that she's part of his world. She might put on his shirt before going to meet his family, for example, as a sign of respect and acceptance of their relationship and his vampire lifestyle.
In the fanfiction, it could be that Edward's clothes have a special scent that attracts Bella. So she wears them because she likes the way they smell. It's a very intimate detail that can add a lot of depth to their relationship. She might steal one of his sweaters and keep it in her room to smell it when she misses him.
Well, perhaps Ginny is trying to make Harry jealous by wearing his clothes in a fanfiction. She might put on his old Gryffindor scarf and walk around the common room, catching Harry's eye. Or, in a more adventurous scenario, Ginny has to disguise herself as Harry for some reason and has to wear his entire set of clothes, which leads to all sorts of comical and dangerous situations as she tries to act like him.
Perhaps in the fanfiction, McGee wears Tony's clothes as a joke among the team. The others initially laugh but then notice how different McGee looks and acts while wearing them. It could lead to some humorous banter and self - discovery for McGee.
Perhaps in a situation where they are in a hurry and Sakura has no other option but to put on Sasuke's clothes. This could lead to some interesting interactions when Sasuke sees her in his attire, like a moment of surprise and then a newfound closeness as they share a laugh about it.
One possible scenario could be that it's for a school play. Maybe Hogwarts is putting on a production where they need boys to cross - dress, and Harry is roped into wearing girl clothes for the role. It could add a comical element to the story as his friends react to his new look.
One possible scenario could be that they travel the world together. They visit different places, experiencing new cultures. Edward could show Bella all the beautiful and historical places he has seen over the years. Another could be that they focus on building a family. They might face challenges like protecting their family from other vampires or supernatural threats. Also, they could be involved in the vampire community more, working towards better relations between different vampire clans.
In certain 'Bella dies in Edward's arms' fanfictions, it might be related to time - travel elements. Imagine a situation where Bella travels back in time to change something for the better in Edward's past, but in doing so, she disrupts the timeline in a way that causes her own death. When she returns to the present (or what was the present before the time - travel), she is already dying and Edward holds her as she passes away. Another idea could be that Bella's human frailty, combined with the dangerous vampire world she's a part of, leads to her being in a situation where she can't be saved, and Edward has to watch her die in his arms.
One scenario could be that Edward accidentally endangers Bella's family in the fanfiction. Since Bella is very protective of her family, this could be a major turning point for her feelings towards him. For instance, if his vampire nature attracts some dangerous vampires to Forks and they target her family.
One possible scenario could be that Bella meets a new vampire who has a very different charm from Edward. Maybe this new vampire is more carefree and shows Bella a different side of the vampire world that she becomes attracted to, leading her to cheat in the fanfiction.
One interesting scenario could be that Stiles wears Derek's clothes to feel closer to him. Maybe Derek has gone away for a while, and Stiles misses him. Wearing his clothes gives Stiles a sense of comfort and connection.
One possible scenario could be that Bella is initially terrified but then realizes there's a deeper connection to Edward's bite. Maybe it unlocks some sort of hidden power within her. Another could be that Edward immediately regrets his action and tries to reverse the effects. It could also be that the bite sets off a chain of events in the vampire community, as it's an unexpected and early bite.