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 might be initially shocked. After all, she would have trusted her friends a great deal. Then she could become very sad and withdrawn. She might throw herself into her studies even more as a way to cope, trying to distract herself from the pain of losing her friends.
She might be initially shocked and hurt. Hermione is a character who values her friendships deeply, so their sudden departure would be a big blow. She could spend some time in denial, not believing that they would actually leave her.
Harry and Ron would probably be very worried. They'd rush to her side immediately. Harry might use his skills to try and find a way to heal her quickly, while Ron would be freaking out a bit but also trying to be helpful.
She might withdraw. Hermione could become quiet and start spending more time alone, like going to the library even more often than usual. This is her way of protecting herself from further hurt.
Hermione could also get angry. She's a strong - willed character. So, instead of just accepting the situation quietly, she might confront her friends and demand to know why they are ignoring her. This could lead to a big argument or a revelation about what's really going on.
She might be initially shocked. But being Hermione, she would quickly gather her wits and start planning. She could use her vast knowledge of magic to find her way or to signal her friends.
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.
She might initially be defensive. Hermione is proud of her intelligence and actions, so she could start by trying to justify what she did. For example, she could say that she was only trying to help or that she had good intentions.
Hermione could also try to reason with Draco. She'll probably start a conversation, trying to understand his motives for capturing her. She might appeal to his better nature if she believes he has one, or try to make him see the error of his ways by using her logical arguments.
Well, Sakura could also try to understand why her friends betrayed her. She might be the kind of character who looks for the root cause of the problem. She could approach her friends, not to forgive them right away, but to have a conversation. By doing this, she hopes to find out if there was some misunderstanding or if they were forced into betraying her.