It depends on how the author writes it. If it's very graphic and violent, it might not be suitable for younger readers. But some authors can handle the dark theme in a more tasteful and less disturbing way.
One possible motive could be jealousy. Bellatrix is extremely loyal to Voldemort, and Hermione is a very powerful and intelligent witch from the side opposing Voldemort. Bellatrix might see Hermione as a threat and also be jealous of the attention Hermione gets from Harry and Ron. So, she tortures Hermione to try and break her spirit and prove her own superiority.
Well, Bellatrix is a very complex and cruel character. In the fanfiction context, she might torture Draco to assert her dominance. She is a powerful and deranged Death Eater, and by torturing Draco, she can show that she is in control. Also, it could be related to her pure - blood mania. If she thinks Draco is not living up to the pure - blood standards in some way, she may take it upon herself to 'correct' him through torture.
Hermione's resilience can also be shown by her not breaking down easily. She might endure the pain and still taunt Bellatrix, showing that she is not afraid. This could be portrayed by her making sarcastic remarks despite the torture. Another way is that after the torture, she quickly recovers and is more determined than ever to fight back.
Sure. There could be. For example, in some fanfictions, the 'torture' might be more of an emotional or mental kind. Bellatrix could use her intimidating presence and cruel words to torment Draco. This type of story can be interesting as it delves into the complex family dynamics within the Death Eater world. It can show how Draco tries to cope with such a difficult situation, perhaps by seeking help from unexpected allies like some of the Hogwarts students who oppose the Death Eaters.
Maybe introduce a deus ex machina element. For instance, just when it seems the torture is getting too much, a powerful magical creature appears and scares Bellatrix away. This would lighten the mood a bit and prevent the story from going into extremely dark territory. Also, the author could play with the idea of Hermione having some sort of pre - prepared magical protection that lessens the impact of the torture.
It makes the story's tone much darker. Hermione being tortured is a very cruel and disturbing event. It can heighten the sense of danger in the plot. For example, it might make Harry and Ron more determined to fight against the Death Eaters. It also shows the brutality of the villains like Bellatrix.
In Hermione and Bellatrix fanfiction, the power dynamic is often an interesting point. Bellatrix has a great deal of power as a Death Eater, but Hermione has her own kind of power in her knowledge and magic skills. Some fanfictions may show a battle of wills between them, where Hermione refuses to be intimidated by Bellatrix's threats. This can lead to some really intense and exciting storylines, like when Hermione stands up to Bellatrix in a duel - like situation in a magically - created arena within the fanfic's plot.
One possible aspect of Hermione and Bellatrix fanfiction could be the exploration of their opposing natures. Hermione is a studious, rule - following Gryffindor, while Bellatrix is a wild and chaotic Death Eater. Fanfiction might play with the idea of how they interact in different scenarios. For example, in a scenario where Hermione is captured by Bellatrix, their exchanges could be filled with tension and power plays. Hermione's intelligence could be pitted against Bellatrix's brute force and loyalty to Voldemort.