Maybe a jealous wizard or witch within the Ministry of Magic. They might be envious of Hermione's popularity and influence among the younger wizards. So they fabricate evidence against her to get her locked up in Azkaban.
Well, perhaps in the fanfiction, Hermione is wrongly accused of a serious crime like dark magic use. Maybe some powerful and corrupt wizarding figure wants to silence her for her Muggle - born rights activism. So they frame her and she gets sent to Azkaban.
One possible plot could be that Hermione is wrongly accused of a serious crime against the wizarding world, perhaps a dark magic related offense that she didn't commit. As a result, she is sent to Azkaban. Inside Azkaban, she has to deal with the Dementors and the harsh prison environment. Meanwhile, her friends Harry and Ron believe in her innocence and start to investigate to find the real culprit and clear her name.
One possible plot could be that Hermione was wrongly accused of a serious crime against the wizarding world. Maybe she was framed by a dark wizard who wanted to silence her for her intelligence and knowledge. She might be struggling to prove her innocence from within Azkaban while her friends on the outside, like Harry and Ron, are desperately trying to find evidence to free her.
One possible plot could be that Hermione discovers a dark secret about Azkaban. And the Ministry of Magic, fearing she'll expose it, sends her there. In Azkaban, she meets some other wrongly imprisoned witches and wizards. Together, they plan an escape while also trying to expose the real criminals in the wizarding world.
Hermione might become more morally ambiguous. Normally she is a very just and rule - following character, but by tricking Draco into Azkaban, she steps into a grey area. She could start to question her own actions and feel guilty.
Harry Potter, of course. His friendship with Hermione is a crucial part of the original story, and in a fanfiction, their bond can be explored even deeper. Maybe Harry discovers a new side of Hermione during the events of Prisoner of Azkaban.
One consequence could be a change in the public's perception of Hermione. Some might see her as a hero for standing up against an unjust imprisonment, while others might view her actions as traitorous, especially if they believe Draco was truly guilty. This could create a divide among the wizarding community.
A group of Death Eater sympathizers within the Ministry could be the main antagonists. They still hold onto the old pure - blood supremacist ideals and see Hermione, a Muggle - born witch, as a threat. So they fabricate evidence against her and send her to Azkaban to send a message to all Muggle - borns that they are not welcome in the new wizarding order they are trying to create.
There could be a group within the Ministry of Magic itself that is corrupt. They might not like Hermione's progressive ideas about the treatment of house - elves and other non - human magical creatures. So they conspire to put her in Azkaban to silence her and maintain the status quo.