For Bella, a nightmare could involve her not being able to control her vampire instincts and accidentally harming someone she loves, like her father or one of her human friends. This would be a huge source of distress for her. Carlisle might have a nightmare where the Cullen family is ostracized by the vampire community for some reason, like breaking an important vampire law. He would be devastated as he has worked so hard to build a harmonious existence for his family within the vampire world.
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 idea could be Carlisle having to protect Bella from a new vampire threat that is specifically targeting her for her unique connection to the Cullens. Maybe a group of nomadic vampires who are jealous of the Cullens' lifestyle.
A possible plot could be that there is a threat to the vampire community that only Bella and Carlisle, with their combined skills and knowledge, can solve. As they work together, they start to see each other in a different light. Carlisle might see Bella not just as a young vampire but as a strong and intelligent equal, and Bella could gain a deeper respect for Carlisle's wisdom and experience. During this time, their relationship could evolve in unexpected ways, like a deeper friendship that is on the verge of something more, but they are hesitant due to the age gap and their different roles in the vampire family.
One interesting plotline could be Carlisle training Edward and Bella to better control their vampire powers. This would involve a lot of interaction between the three characters, with Carlisle using his experience to guide them. Another could be them facing a new vampire threat together, where Carlisle's leadership, Edward's abilities, and Bella's unique perspective as a former human come into play.
Perhaps in the fanfiction, Bella has a life - threatening situation and Carlisle, in his attempts to save her, becomes overly involved and his feelings cross a line. Esme, being the perceptive one, notices the change in Carlisle's behavior towards Bella. This could then set off a chain of events where the Cullen family has to choose sides or work to reconcile Carlisle and Esme.
In some fanfictions, Bella might get hurt during a fight with a rogue vampire. For example, she could be caught off - guard while trying to protect someone in Forks. Another scenario could be when she is exploring the woods alone and stumbles upon a dangerous supernatural creature that attacks her.
In 'bella gets hurt fanfiction', one possible scenario could be that Bella gets physically injured during a fight with a supernatural being, like a vampire. Another could be she gets hurt accidentally while exploring a dangerous place.
One possible scenario could be that they are so preoccupied with the affairs of the vampire community outside their family that they unintentionally neglect their relationship. For example, Carlisle might be spending a great deal of time trying to maintain a truce with a rival vampire group, while Esme is focused on helping other vampires in distress. This leaves little time for them to nurture their own bond, and in the fanfic, it could lead to a rift between them.
Well, in this type of fanfiction, it might be that Twilight Sparkle is betrayed by a mentor figure. This mentor could have been teaching her false information all along, causing her to make mistakes that put her and her friends in danger. Or it could be that she is betrayed in a love - related situation. For example, if she has feelings for a certain pony and that pony pretends to reciprocate only to use her for something else, like getting access to the library in Canterlot. There are so many directions this fanfiction could take.
One possible scenario could be that Edward sacrifices himself to save Bella from a powerful new vampire threat. Another might be that he succumbs to an illness that vampires in this fanfic world are suddenly vulnerable to. Or perhaps he is killed in a battle against a group of werewolves gone rogue.