One possible plot could be that Hermione's friends start believing false rumors about her. For example, they might think she's been stealing potions ingredients for personal gain when in fact she was framed. As a result, they shun her and exclude her from their group activities. This makes Hermione feel isolated and betrayed, and she has to find a way to clear her name and either regain her friends' trust or find new allies.
In a 'Hermione betrayed by her friends' fanfiction, it could be that her friends are influenced by a new and charismatic student who has a vendetta against Hermione. This new student convinces Hermione's friends that she is a bad influence. So, they begin to ignore her and even go as far as to undermine her in class. Hermione is left heartbroken but uses this as an opportunity to grow and show her true strength, not relying on those who have so easily turned their backs on her.
Perhaps her friends become jealous of Hermione's academic success. They could start spreading lies that she's been using dark magic to enhance her knowledge. Her so - called friends then side with those who are against her. Hermione, being the strong - willed character she is, decides to prove them wrong on her own, all while dealing with the pain of betrayal. She might start to focus more on her own research and self - discovery, away from the group that once called her a friend.
She might initially be in shock. Hermione is used to relying on her friends, so the betrayal would be a huge blow. She could then become angry and start to isolate herself. In some fanfictions, she might try to figure out why they did it on her own, using her intelligence to uncover the truth.
Another possibility is that Fleur, in a bid to gain more influence in the magical world, uses Hermione's research on some ancient magic without permission. When Hermione finds out, she realizes Fleur has been using her all along, and this is the ultimate betrayal. Hermione then has to find a way to expose Fleur's actions and clear her own name.
It could be that an external force, like a dark wizard in disguise, is the main antagonist. This dark wizard targets Hermione because of her potential to be a great threat to their evil plans. They use magic to cloud the minds of her friends, making them believe Hermione is up to no good. The friends, being under this spell, betray Hermione without realizing they are being manipulated. The dark wizard then watches as Hermione struggles with this betrayal, all part of their grand scheme.
It could be that a member of the Order, out of jealousy or a wrong perception of Hermione's power, convinces the others that she is a liability. So, they betray her by not believing in her when she discovers something important or by preventing her from using her skills to help. Hermione, being the strong - willed character she is, would then strive to prove them wrong and expose the real issues within the Order.
One possible reason could be jealousy. Maybe her friends are envious of Hermione's intelligence and magical abilities. In a fanfiction, this could lead them to betray her to gain an advantage or to make themselves look better. Another reason might be a misunderstanding. A miscommunication or false assumption could cause her friends to turn against her.
One way it could develop is if Dumbledore withholds important information from Hermione about her family or her own magical abilities. He might do this because he fears she will use that knowledge in a way that could disrupt his grand plan for the wizarding world. For instance, Hermione discovers she has a special power that could defeat Voldemort easily, but Dumbledore has kept it from her all along, making her feel extremely betrayed as she could have saved many lives if she knew earlier.
In such a fanfiction, perhaps Harry's friends are jealous of his newfound powers or popularity within the wizarding world. So they spread rumors about him being untrustworthy. As a result, Harry is shunned by many in the community. He has to embark on a solo journey to prove his innocence and in the process discovers who his true friends really are.
One possible way this could develop is through a misunderstanding. Maybe Naruto is framed for a crime he didn't commit, and his friends believe the false evidence against him. For example, an enemy could plant evidence that makes it seem like Naruto is working with the villains. His friends, not knowing the truth, turn their backs on him. This would lead to Naruto feeling extremely hurt and isolated, and he might have to go on a journey to prove his innocence on his own.
In a fanfiction where Naruto is betrayed by his friends, it could start with jealousy. Suppose Naruto gets a great power or a special recognition. His friends, feeling overshadowed, might be tricked by an evil force into thinking Naruto is using them. So they betray him, which makes Naruto realize that he has to rely on his own strength and find new allies who truly understand him.
In a 'Twilight Betrayed by Her Friends' fanfiction, it could be that Twilight's friends become jealous of her powers. They feel overshadowed by her abilities and knowledge. So they start to undermine her at every turn. For example, they might ruin her chances of getting a special magical promotion or getting into an exclusive magical study group. Twilight is heartbroken at first but then decides to prove herself without their support and in the process, she might find new friends who truly appreciate her for who she is.