Luna could be another ally. Luna has a unique perspective and is very perceptive. She might see the situation in a way that others don't and could help Hermione in her revenge. Luna's ability to think outside the box and her disregard for some of the traditional wizarding norms could be very useful when going against the Order.
Neville could also be an ally. He's grown a lot in courage and skill. He might join Hermione if he believes the Order has done something wrong. Neville has his own reasons to be distrustful of some in authority, so he could be a great support for Hermione in her revenge plot.
Harry and Ron could be her obvious allies. They've been through so much together, and if Hermione has a reason to get revenge on the Order, they'd likely stand by her side. They trust her judgment and would be willing to help her out.
Maybe Ron accidentally ruins Hermione's important experiment in the wizarding lab. In the fanfiction, Hermione could get revenge by getting all their mutual friends to side with her in an argument. She could present all the facts about how Ron's carelessness has cost her time and effort, making Ron feel isolated and guilty.
His friends like Ron and Hermione could be his allies. They have always stood by Harry and if Harry believes that Dumbledore has wronged him, they might side with him. Ron, with his loyalty and Hermione with her intelligence could help Harry plan and execute his revenge. They could use their knowledge of magic and Hogwarts to find ways to undermine Dumbledore's influence.
Harry Potter could be involved. He might be caught in the middle of Hermione's revenge plan on Ron. He could try to be the peacemaker, but his attempts might backfire, leading to more chaos between the two. For example, he might accidentally reveal Hermione's plans to Ron, making Hermione even more determined to succeed with her revenge.
Neville could be an ally too. His skills in herbology could come in handy when it comes to finding the right plants to feed the dragons or to use for medicinal purposes. Also, Luna Lovegood might be involved. Her unique perspective and knowledge of strange magical creatures could give Hermione new ideas on how to care for the dragons. She might know of some obscure spells or methods that are beneficial.
It could be Draco Malfoy. In some fanfictions, Draco might be pushed to such an extreme by his family's beliefs that he resorts to physical violence against Hermione. He might punch her out of jealousy or to assert his so - called superiority.
Ron could be a main character. He might be the first one to notice Hermione's new haircut. He could have a really strong reaction, like blushing because he suddenly finds her even more attractive with the new look. And their relationship could develop further because of this change in her appearance.
Obviously, Harry would be the central character. He's the one seeking revenge. Hermione would also likely be involved. She might be torn between her loyalty to Harry and her belief in the Order. If she sides with Harry, she could use her intelligence to help him in his revenge plot, like coming up with elaborate plans to outwit the Order. Ron could also play a significant role. He might initially be against Harry's idea of revenge but then slowly come around as he realizes Harry's reasons.
Harry and Ron could be her main allies. They've always been by her side in the original story, so it's likely they'd support her new adventure as a dragon rider. They could help her keep her dragon - riding activities a secret from the teachers at Hogwarts.
Voldemort himself could be the main antagonist in this scenario. He might offer Hermione something she desperately wants in exchange for her betrayal. Maybe he promises to spare her Muggle - born friends if she gives up the Order's plans and secrets. His powerful and intimidating presence could easily force Hermione into a difficult situation where she feels she has no choice but to betray.
There could also be some new characters. Maybe a wizard or witch who works in a wizarding fashion store where Hermione gets her new clothes. This character could give her advice on what styles would suit her best and become a sort of friend during her makeover process.