One way it could develop is if Dumbledore withholds important information from Hermione about her family or her own magical abilities. He might do this because he fears she will use that knowledge in a way that could disrupt his grand plan for the wizarding world. For instance, Hermione discovers she has a special power that could defeat Voldemort easily, but Dumbledore has kept it from her all along, making her feel extremely betrayed as she could have saved many lives if she knew earlier.
Dumbledore might be motivated by his over - arching plan to defeat Voldemort. He could see Hermione as a sacrifice that needs to be made. Maybe he believes that by betraying her, he can gain some crucial information from the enemy that will ultimately lead to Voldemort's downfall.
In the fanfiction, the plot might develop with Hermione secretly investigating Dumbledore. She could enlist the help of other characters who also have doubts. As she uncovers more secrets, her distrust grows, and this causes a rift within the group of friends. Some might side with her, while others still believe in Dumbledore. This creates a lot of tension and conflict as they try to deal with the threat of the dark side while also dealing with their internal differences.
Their relationship could start off with a lot of tension. Snape has always had a bit of a prickly relationship with students, especially those he sees as being too much like Gryffindors. However, as they are forced to collaborate, they might find common ground in their love for knowledge. Snape is a highly skilled wizard in many areas, and Hermione is eager to learn. This shared interest could be the starting point for a more amicable relationship.
There could be. Fanfiction writers love to explore different scenarios that deviate from the original story. But it's important to note that this goes against the general perception of Dumbledore's character. In the official Harry Potter series, Dumbledore is a protector, not a kidnapper. But in the world of fanfiction, anything is possible.
Another possibility is that Fleur, in a bid to gain more influence in the magical world, uses Hermione's research on some ancient magic without permission. When Hermione finds out, she realizes Fleur has been using her all along, and this is the ultimate betrayal. Hermione then has to find a way to expose Fleur's actions and clear her own name.
Hermione's character often becomes more confident. Since she has knowledge of the future, she can take more risks and be bolder in her actions. For example, she might be more assertive in her interactions with teachers or other powerful wizards.
One possible plot could be that Hermione discovers a hidden family secret that reveals she is Dumbledore's sister. This leads to her having access to new knowledge and powers that Dumbledore left for her, which she uses to fight a new dark force in the wizarding world.
One possible plot could be that Dumbledore has been possessed by a dark entity. Under its influence, he kidnaps Hermione thinking she has some knowledge or power that the entity wants. Hermione then has to use her wits to try and break Dumbledore free from the possession while also trying to escape.
It could be that a member of the Order, out of jealousy or a wrong perception of Hermione's power, convinces the others that she is a liability. So, they betray her by not believing in her when she discovers something important or by preventing her from using her skills to help. Hermione, being the strong - willed character she is, would then strive to prove them wrong and expose the real issues within the Order.
In some fanfictions, Dumbledore might be portrayed as betraying Harry by withholding crucial information. For example, if he knew more about Harry's fate or the true nature of the threats he faced but didn't share it all. This could make Harry feel betrayed as he was left in the dark and had to face greater danger without full knowledge.