One consequence could be that she is forced to perform dark magic against her will. This would be a huge moral struggle for her, as Hermione is a firm believer in the light side of magic. It could also change her perception of herself and her magic abilities in a very negative way.
She could face legal issues in the wizarding world. Killing is not taken lightly, even if it's Death Eaters she's killing. There might be a trial to determine if her actions were justified. If the wizarding authorities are corrupt or influenced by the wrong people, she could even be wrongly convicted.
One possible reason could be Hermione's intelligence. In the Harry Potter series, she is extremely smart, and the Death Eaters might be intrigued by someone with such powerful intellect in a fanfiction scenario. They could see her as a valuable asset or a challenging target.
Well, it could start with Hermione being kidnapped by the Death Eaters at a young age. She might be forced to attend their dark magic lessons. However, she uses her intelligence to learn about their weaknesses. For instance, she could discover a flaw in the security spells around their lair. And then, as she grows up, she could start to subtly manipulate the Death Eaters into fighting among themselves, all while pretending to be a loyal follower.
Perhaps in the fanfiction, Hermione has something that the Death Eaters are after, like a powerful magical artifact. They fight over who gets to take her prisoner first in order to extract the location of this artifact from her. It could also be that they are under the orders of Voldemort to capture her alive, but they start fighting among themselves due to personal rivalries and the desire for glory within the Death Eater ranks.
A possible plotline could be that a Death Eater discovers Hermione has knowledge of a powerful spell or magic item that could help them overthrow Voldemort. So, they save her to get that information. For example, she might know of a way to break a powerful curse that Voldemort has placed on them.
Well, she could end up in a duel with a powerful Death Eater. Hermione is a very skilled witch, so it would be a great show of her magical abilities. Maybe she discovers a new spell during the fight that helps her gain the upper hand.
She could use her intelligence. Maybe she could pretend to cooperate while actually looking for loopholes in their plans or trying to send hidden signals to her friends. For example, she could subtly mislead them about the location of important items or people.
One popular 'Hermione forced by Death Eaters' fanfiction might be 'The Darkest Times'. In this type of fanfiction, often the story explores Hermione's strength and resourcefulness in a really difficult situation. The plot usually involves her having to outwit the Death Eaters who are trying to force her into doing their bidding, whether it's for information or some dark magic purpose.
Maybe Hermione discovers that one of the Death Eaters training her has a change of heart. This Death Eater then starts to help Hermione escape or undermine the other Death Eaters from within the group. It adds an interesting layer of complexity to the story.
One possible plotline could be a story of redemption. Maybe a Death Eater starts to question their beliefs after getting to know Hermione on a deeper level. For example, they could be forced to work together on a mission and gradually see the good in her, leading to a change in their ways.