She could become defensive at first. After all, she's being unjustly targeted. She might start to isolate herself a bit from the Gryffindor group while she tries to find a solution. Hermione would also likely use her vast knowledge to research if there are any spells or external forces causing this. She might also seek help from other houses, like Ravenclaw, where her intelligence would be more appreciated in this situation.
Hermione would be determined to prove her innocence and worth. She would gather evidence if it's a case of false accusations. If it's a matter of differences in ideology, she would try to have a rational debate with those who oppose her. And if it comes down to it, she might even stand up against the whole Gryffindor house to defend what she believes is right, showing her true Gryffindor - like courage in the face of adversity.
In some fanfictions, it could be that Hermione starts to question and challenge long - held Gryffindor traditions. Gryffindors are often seen as brave and a bit reckless, while Hermione is more rational. Her attempts to bring in more caution or different ways of thinking might be seen as going against the Gryffindor spirit by some of her housemates. Also, if there's a power struggle within the Gryffindor house, Hermione's intelligence and influence could be seen as a threat by those who want to be in control.
Hermione could also be more understanding in some fanfictions. If she senses that there's something deeper behind Draco's actions, she might try to calm the situation down. She could ask him why he did it instead of immediately retaliating. Maybe she sees a glimmer of vulnerability in his eyes and decides to approach the situation in a more empathetic way. This could then lead to a conversation that changes their relationship for the better.
Often, Hermione reacts with a mix of shock and anger. She's a strong - willed character, so she doesn't just take it lying down. In some fanfictions, she immediately confronts the cheater and gives them a piece of her mind.
Hermione would probably be defiant at first. She's not one to take injustice lying down.
Hermione could become withdrawn. She might isolate herself from her friends for a while, spending her time in the library trying to make sense of it all. She might also feel a sense of betrayal, especially if they had some sort of understanding or relationship developing.
She might initially be shocked and scared. But then she would start to think rationally and try to find a way to outwit Snape. For example, she could start to gather evidence against Snape's own wrongdoings, if there are any, so that she can turn the tables on him.
After the initial reactions, Hermione may choose to isolate herself for a while to figure things out. She would use this time to study and research, trying to find a solution to the problem with her friends. She might also look for new allies or resources within the fanfiction world to help her deal with the situation.
She could get angry. Hermione, being the strong - willed character she is, might feel betrayed that Harry is leaving. She might yell at him, asking him why he's doing this and how he could leave her after all they've been through together. Her anger is really a mask for her deep sadness and fear of losing him.
She might be initially confused. Hermione is a logical person, and without an obvious reason for Harry's silence, she would be at a loss. She would probably try to think back on their recent interactions to figure out what went wrong.
She might be initially shocked. After all, Draco is usually seen as this tough Slytherin. But then she could feel sympathy. For instance, she might offer him a handkerchief without saying much at first.