One possible plot could be that there is some sort of misunderstanding. Fleur believes Hermione is in danger from some dark magic or a dangerous creature and ties her to the bed to keep her safe. As the story unfolds, they realize the miscommunication and work together to solve the real issue at hand. However, this is a rather strange starting point for a plot and would need a lot of careful development to make it a believable and engaging fanfiction.
One possibility could be a situation where Fleur is under the influence of a dark spell. Maybe she's been hexed to do this to Hermione. In the fanfiction world, this could be a lead - up to a rescue mission by Harry and Ron. They would have to figure out how to break the spell on Fleur and free Hermione.
I'm not aware of such a specific fanfiction. Fanfiction can cover a wide range of themes and scenarios, but this one seems rather unusual and perhaps not in line with the general spirit of the original works. However, the world of fanfiction is vast, and there could potentially be something out there that I haven't come across.
It could be a case of miscommunication. Fleur misinterprets something Hermione said or did, and in a fit of rage or confusion, she ties Hermione to the bed. As the story progresses, they clear up the misunderstanding and end up becoming friends or allies.
One plotline could be that they are victims of a prank by some mischievous students using a new, untested spell. They then have to figure out how to break free and also how to deal with the fallout of being in such an embarrassing situation together.
Well, it could develop into a story of deep friendship. Maybe Fleur was trying to comfort Hermione during a difficult time. They might start sharing their secrets and fears, and through this physical closeness, a strong bond of sisterhood could form.
Well, it could be a story about Percy being held captive by some villain who ties him to the bed frame as a way to keep him from escaping or causing trouble. Maybe the story then revolves around Percy trying to free himself and defeat the villain.
One possible reason could be that she was captured by some dark wizards who oppose her and her friends' actions. They might see her as a threat due to her intelligence and magical abilities. Another reason could be related to a misdirected spell or curse. Maybe someone was aiming for another target but accidentally hit Hermione and then tied her up to prevent her from seeking help immediately.
One possible plot could be that the mom has some sort of a secret that someone wants to keep her from revealing. So they tie her to the bed to stop her from going to the authorities or telling someone important. For example, she might have witnessed a crime and the criminals tie her up to keep her quiet.
One possible plotline could be Fleur struggling with her feelings. She might be in a situation where she has to interact with Hermione a lot, like during some magical events or projects at Hogwarts or in the wizarding world. And she gradually realizes that her feelings are more than just friendship.
One possible plot could be that Hermione, as a Lycan, struggles to hide her identity within the Hogwarts community. Fleur, being perceptive, might notice something off about Hermione. Maybe Hermione is afraid of being discovered and ostracized, while Fleur, having her own experiences with being different (as a Veela), tries to help Hermione come to terms with her new lycanthropy. They could form a strong bond as they both deal with the challenges of being 'other' in the wizarding world.