On the positive side, the betrayal could make her stronger. She is a very determined character. This experience might fuel her to fight back against those who wronged her. She could use her intelligence to expose the betrayer and their motives, and in the process, become a more powerful and respected figure at Hogwarts. Also, it might make her more careful in choosing her allies in the future.
Hermione could isolate herself. The pain of betrayal might make her want to withdraw from social interactions at Hogwarts. She might focus more on her studies and her own personal growth, thinking that relying on others only leads to disappointment. She could also start to be more secretive about her plans and ideas, fearing that they will be used against her again.
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.
Hermione might seek revenge. Given her intelligence and magical abilities, she could use her skills to get back at Harry and Ron for their betrayal. This could lead to a big rift in their friendship and even endanger their common goals in the wizarding world. She might also side with other characters who are against Harry and Ron, changing the whole dynamic of the story.
She might become more distrustful. After being betrayed, it's natural for her to have a hard time trusting others again.
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.
Voldemort may also try to extract information from her. Given Hermione's vast knowledge, he might think she knows secrets about the Order of Phoenix or Dumbledore's plans. He could use various dark magic methods to force her to talk.
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.
She might gain some vampire - like abilities such as enhanced strength, speed, and senses. For example, she could be able to run faster than normal wizards and have better night vision.
Mrs Black could be so offended that she starts to plot against Hermione. For example, she might try to get Hermione into trouble with the Hogwarts authorities by spreading false rumors about her.
She could face legal issues in the wizarding world. Killing is not taken lightly, even if it's Death Eaters she's killing. There might be a trial to determine if her actions were justified. If the wizarding authorities are corrupt or influenced by the wrong people, she could even be wrongly convicted.
Well, for Harry, it would be a huge emotional blow. He trusts Hermione deeply, so her betrayal could make him question his own judgment. It might also make him more isolated as he loses one of his closest allies. For the wizarding world, if Hermione was on the wrong side, it could lead to chaos as she is very intelligent and powerful. Her knowledge of spells and magic could be used against the good side.
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.