She would probably be more sophisticated in her appearance and mannerisms. Growing up with the Malfoys, she would be used to a certain level of luxury and propriety. But internally, she would be constantly struggling with the moral implications of the Malfoy ideology. Her relationships with her friends, especially Harry and Ron, would be very different. There would be a lot more tension and mistrust at first, as they come from opposing 'worlds' in a sense. It would be really interesting to see how she would break free from the Malfoy - influenced mindset and find her true self again.
One plot twist could be that Hermione discovers she has a hidden connection to the Malfoy family, like she's a long - lost relative. This would add a whole new layer to her being raised by them. Another could be that she uses her knowledge of both the Gryffindor and Malfoy ways to broker peace between the two factions in the wizarding world that are often at odds. Maybe she uncovers a secret plot within the Malfoy family that goes against her new - found loyalty to them, forcing her to choose between her upbringing and what she believes is right.
She would probably become more guarded and secretive. In the original story, Hermione is quite open with her friends about her thoughts and feelings. However, in the Malfoy household, she'd have to hide a lot of her true self. Her character development might see her becoming a master of deception, pretending to go along with the Malfoy's views while secretly working against them. This would add a whole new layer of complexity to her personality as she tries to balance her true self with the persona she has to present to the Malfoys.
She becomes more confident. With Sirius' boldness and Remus' intelligence guiding her, she's more willing to take risks. For example, in some fanfictions, she might be more likely to stand up to bullies at Hogwarts.
In some fanfictions, Hermione might be related to the Malfoys through a complex family secret. For example, there could be a long - lost family connection that was hidden for years. Maybe an ancestor from Hermione's family had a relationship with a Malfoy in the past, which led to some sort of blood - related connection that only gets revealed in the fanfiction world. This connection then changes the dynamics between Hermione and the Malfoys, leading to interesting plot twists and character developments.
He might be more arrogant. Growing up with the Malfoys, he'd be used to thinking his family was superior. He'd lack the humility Harry in the original series has.
In such a fanfiction, Hermione's character could become more rebellious. Sirius has a wild streak, and growing up with him might make Hermione less likely to blindly follow the rules. She could be more confident in taking risks and standing up for what she believes in.
Hermione is the central figure who drives much of the action. Her interactions with the Malfoys are what the fanfiction is often centered around. The Malfoys, with their Slytherin traits, contrast with Hermione in many ways. Their different beliefs and values create the basis for a lot of the drama and character development. Whether it's Draco's initial hostility towards Hermione or Lucius' attempts to maintain the family's status in the face of Hermione's presence, these characters are essential to the story.
It would likely make her more self - assured. Sirius would constantly be there to support her and tell her she's capable. This could lead to Hermione being even more outspoken and confident. Instead of just arguing her points in the classroom, she might start challenging the wizarding world's old - fashioned ideas more publicly. Also, she might develop a stronger sense of loyalty to those she cares about, like Sirius, similar to the loyalty he showed to his friends.
It would likely be a very different story. Harry might grow up with the pure - blood supremacist views of the Malfoys. He could be trained in dark magic - adjacent skills. His relationships would be flipped, for example, he might be enemies with Ron and Hermione who are seen as 'blood traitors' by the Malfoys.
One interesting plotline could be Hermione and the Malfoys having to work together on a secret magical project. Maybe it's something that could change the wizarding world, and they have to put aside their differences.