She might become more distrustful. After being betrayed, it's natural for her to have a hard time trusting others again.
Hermione could face isolation. If she has been betrayed by those in the 'light', she may be shunned or left alone as others side with her betrayers. Also, she might lose her confidence in her own beliefs and actions. Since she was betrayed by those who were supposed to be on the same side as her, she may start to doubt if she has been doing the right thing all along. And she could be in great danger. Her betrayers might expose her secrets or put her in harm's way, either directly or indirectly.
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 question the motives of those around her, even her closest friends.
It depends on the specific plot of the fanfiction. It could be a friend who turns against her due to jealousy, or perhaps a false ally within the so - called 'light' side who has ulterior motives.
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.
Perhaps there is some sort of political intrigue within the 'light side'. There could be factions that see Hermione as a threat to their own power and influence. So, in order to maintain their position, they choose to betray her.
Well, it could be that Draco betrays Hermione's academic trust. Since they are in a world where magic and knowledge are highly valued, he might steal her research or ideas for a spell or a magical discovery. This would be a huge betrayal as Hermione values her intellectual pursuits greatly. Also, he could betray her trust regarding a secret mission they are on together. He might abandon her in a dangerous situation, like in a dark forest full of dangerous magical creatures or in an old, enchanted castle filled with dark magic traps, just to save his own skin.
Hermione could react by using her intelligence to expose Fleur's betrayal. She might start gathering evidence of what Fleur has done wrong and present it to their mutual friends or to an authority figure in the wizarding world.
In some fanfictions, it could be a misunderstanding that spirals out of control. Hermione and Ron misinterpret one of Harry's actions. For instance, Harry might be trying to protect them in a secret way, but it looks like he's up to something bad. Their lack of trust then grows, and they end up betraying Harry, perhaps by not coming to his aid when he really needs them, which could have serious consequences for Harry.
Another theme is the search for truth. In many of these fanfictions, Hermione is determined to find out why she was betrayed and who was really behind it. It becomes a journey of discovery, not just about the betrayal itself, but also about the people she thought she knew.
I'm not sure specifically as there could be many different interpretations in fanfiction. It might be about a situation where The Order, perhaps in the Harry Potter universe, betrays Hermione in some way, like leaving her in a dangerous situation, or not believing her when she has crucial information.