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.
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.
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 many fanfictions, a plot where Hermione is pregnant at Hogwarts can bring a whole new set of challenges and storylines. It might involve how she manages her studies while dealing with the physical and emotional changes of pregnancy. Also, it could explore how her friends, like Harry and Ron, react to this unexpected situation.
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.
If Hermione transfers to Hogwarts, her relationships would change significantly. For starters, she would have to start from scratch building relationships with her classmates. She might befriend some students who were on the outskirts in the original story. With the teachers, she'd have to prove herself quickly. Some teachers might be more strict with her as a new transfer, while others might be intrigued by her previous magical education. Her relationship with the Gryffindor house as a whole would also be different as she tries to earn her place among them.
In this fanfiction, perhaps Hermione might be even more excited than in the original story. She could start preparing for Hogwarts immediately, reading every book she can find about the school.
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.
In fanfiction, the idea of Hermione being pregnant with twins at Hogwarts can lead to a lot of interesting character developments. Her friends, like Harry and Ron, would likely have to step up and support her. And the Hogwarts faculty might be in a quandary about how to handle a pregnant student. There could also be a mystery surrounding the father of the twins, or perhaps it's a magically - induced pregnancy due to some dark or light magic experiment gone wrong.