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.
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.
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.
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.
In many fanfictions with such a plot, it could be a so - called friend who betrays Hermione perhaps out of jealousy. Maybe they are envious of Hermione's intelligence and popularity at Hogwarts, and for some self - serving reasons, they choose to betray her.
Sakura could become very angry. She has been let down by those she trusted, and anger is a natural response. She might lash out at her friends or distance herself from them immediately. For example, she could say some harsh words to them in the heat of the moment.
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.
Ron is a likely candidate. In the original story, they had their ups and downs, and in fanfiction, it's easy to imagine him doing something that Hermione would see as a betrayal, like not supporting her in her academic pursuits. Another could be Draco Malfoy. He could pretend to befriend her for some devious reason and then turn on her.
In a fanfic, the betrayal might also be a misunderstanding. Her friends could be misled by false information about Sakura. For example, an enemy might spread rumors that Sakura is planning to betray them first, causing her friends to turn against her without really knowing the truth.