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.
She might get revenge because she felt the Order made a decision that put her or her friends in danger. For example, if they sent Harry on a dangerous mission without proper support, Hermione could plan some elaborate scheme to teach them a lesson. Maybe she'd use her intelligence to expose some of their secrets or weaknesses.
Harry and Ron would most likely be her allies. They've always been by her side through thick and thin. Neville could also be an ally as he has shown courage and a willingness to stand up for what's right. Luna might be another one. Her unique perspective on things could be really helpful in a rebellion.
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.
Sasuke could be an ally. He also has his own issues with Konoha and would understand Naruto's need for revenge. They could combine their powers, with Naruto's massive chakra reserves and Sasuke's unique Sharingan abilities.
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.
Another powerful mage from a rival guild. This mage could see Lucy's revenge as an opportunity to weaken Fairy Tail and offer their assistance.
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.
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.
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.
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.