Well, her friends would surely miss her a great deal. Harry and Ron would feel like they've lost an important part of their team. Academically, the Gryffindor house might see a decline in grades as Hermione was often the one helping others study. Also, the teachers might be disappointed as she was a brilliant student.
One possible reason could be that she's frustrated with the school's bureaucracy. For example, if she constantly faces obstacles in getting approval for new study groups or advanced classes. Another reason might be a personal quest. Maybe she discovers a hidden mystery outside of Hogwarts that she can't explore while being a student there.
One reason could be that she might be on a secret mission. In some fanfictions, she could be trying to find a powerful magical artifact outside the walls of Hogwarts to save the wizarding world from a new dark threat. She might believe that she can't achieve this while staying within the school's confines.
The students would surely miss her. She's a role model for many, especially the younger students who look up to her intelligence and determination. Without her, the study groups and academic competitions might not be as intense or successful.
She might become more distrustful. After being betrayed, it's natural for her to question the motives of those around her, even her closest friends.
It can completely change the dynamic. For one, it might lead to a new setting. Instead of the familiar Hogwarts corridors, the story could shift to different magical locations where Hermione is now exploring. This can introduce new characters and magical creatures.
Maybe she leaves because of a conflict. It could be with a teacher who doesn't support her unorthodox ways of learning or a fellow student who makes Hogwarts an unpleasant place for her. In fanfiction, there could be a lot of creative interpretations of such conflicts.
The relationships within the village would be severely affected. His friends would be heartbroken and split into groups, some trying to find him, others blaming themselves. The new generation of ninjas would also lack a role model. And the balance of power in the ninja world could shift, as other villages might see Konoha as weakened without Naruto and try to gain an upper hand.
Hermione might go with him. She's always been by Harry's side, and she would likely follow him out of loyalty and also because she might see the value in whatever mission or journey Harry is embarking on. She could provide the intellectual support and research skills that Harry needs.
One consequence could be the destruction of the friendship group. Ron, for instance, would be devastated. He has strong bonds with both Hermione and Harry. His reaction could range from seeking revenge on Hermione to falling into a deep depression. Also, the wizarding world as a whole would be in chaos. Harry was seen as the 'Chosen One', so his death would leave a power vacuum.
In the fanfic, it could have an impact on the relationships between students and teachers. Teachers who oppose Umbridge may secretly encourage students to resist this forced reading. This could strengthen the bond between like - minded students and teachers. On the other hand, students who side with Umbridge may be ostracized by their peers. Also, the forced reading might limit the students' exposure to a diverse range of magical knowledge, as they are stuck with the books Umbridge chooses, rather than exploring a wider variety on their own.