In fanfiction, if Bella has a high fever, first, someone should call for a doctor. The doctor can then diagnose her condition accurately and prescribe the right medicine. Also, her friends or family in the story could cool her down by using a wet towel on her forehead and making sure she drinks plenty of fluids to avoid dehydration.
In fanfiction, it could be her best friend. Her best friend would be really worried and would stay by her side all the time. She would make sure Bella takes her medicine, gets enough rest, and has something to eat and drink.
Perhaps in the fanfiction world, Bella caught a mysterious disease that's specific to that fictional universe. It could also be that she overexerted herself, like using her special powers too much if she has any in the story. Stress can also be a factor. If she's been through a lot of emotional turmoil, like a fight with a loved one or facing a big threat, her body might react with a fever.
In a romantic - themed fanfiction, if there's a love interest, that person would be extremely concerned. They might hold Bella's hand, whisper soothing words, and even sacrifice their own needs to make sure she gets better. Meanwhile, some rival characters might see this as an opportunity to gain an advantage, but most of the good - hearted characters would come together to help Bella through her fever.
Well, it could be about Sonic's friends trying to take care of him while he has a fever. Maybe Tails uses his gadgets to monitor Sonic's condition and Knuckles brings some special herbs that are supposed to help with fevers in their world. And Amy could be fussing over Sonic, making him soup or something.
Well, in a fanfiction where Ash has a fever, it could lead to a lot of different plot developments. Maybe Team Rocket would take advantage of his weakened state and try to steal his Pokémon. But of course, his friends, like Misty and Brock, would be there to protect him. They might search for a special herb or medicine in the Pokémon world to cure his fever.
In the fanfiction, Naruto might have a fever due to overusing his chakra. When he pushes his body to its limits in intense battles or during extensive training, it could strain his body and cause a fever.
Love is a very common theme. Spring often symbolizes new beginnings, so their love might be shown as growing or evolving in these fanfics. Another theme could be nature. Since it's spring, descriptions of blooming flowers, green landscapes, and fresh air are likely, and how they interact with Bella and Edward's relationship.