Draco Malfoy would be a likely character. Since they are in the same house now, they would have more opportunities to interact. Their relationship could start off as hostile as always, but then gradually change as Hermione shows different aspects of herself in Slytherin.
Some of the other Slytherin students who are on the fringe or more interested in learning rather than just pure - blood supremacy. Hermione could attract these students and form a little group within Slytherin. They could study together and support each other in their academic pursuits.
Other pureblood characters like Draco Malfoy would surely interact with her. Given her new status, Draco might be conflicted. On one hand, she's a 'mudblood' in his old view, but now as a rich pureblood, he might have to reevaluate his attitude towards her. And there could be other pureblood families' members who would either befriend or oppose her based on their family politics.
Another development could be her relationship with the other houses changing. The Gryffindors might initially be suspicious of her new Slytherin status. However, Hermione could use this as an opportunity to bridge the gap between the two houses. She could show that just because she's in Slytherin doesn't mean she's abandoned her Gryffindor courage and loyalty.
Harry and Ron are obvious choices. They have a long - standing friendship with Hermione, and their reunion would be filled with reminiscing and new adventures.
If Hermione was sorted into Slytherin, she'd bring a whole new dynamic to the house. Slytherin is known for its ambition and resourcefulness, and Hermione has those traits in spades. She might change the perception of what it means to be a Slytherin. Instead of just being about pure - blood supremacy and cunning for the sake of it, she could introduce a more ethical form of ambition. Her study habits would probably influence some of the other Slytherins to be more studious. And she'd also have to navigate the politics within Slytherin, which could be a real challenge as she's used to the more straightforward environment in Gryffindor.
It could be Draco Malfoy. Despite his past animosity towards Hermione, in the fanfiction, he might have a change of heart. Maybe he realizes that the old pure - blood ideas are wrong and decides to use his Slytherin cunning to protect her. Another character could be Blaise Zabini. He's often portrayed as a bit of an enigma in the original books, and in this fanfiction, he could see Hermione's value and take it upon himself to keep her safe.
Hermione's character development could involve her learning to balance her traditional values with the new ones in Slytherin. She might start to value self - preservation more, as it is a trait often associated with Slytherin. This could make her a more well - rounded witch, not just relying on her Gryffindor - like courage all the time. Draco, on the other hand, could become more empathetic. Seeing Hermione face the challenges of being in Slytherin as an outsider could make him realize how wrong some of his previous actions were, and he could grow to be more inclusive.
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.
Obviously, Harry and Ron would be highly involved. They are Hermione's closest friends. Harry would likely be the one leading the effort to find a solution, given his heroic nature. Ron, on the other hand, would probably be more involved in the day - to - day care of baby Hermione, with his big, caring heart.
Her relationship with Harry and Ron would be strained at first. They might feel betrayed or confused. But over time, if Hermione can show them that she's still the same person, they could reconcile. With the Slytherins, she might start off as an outcast but gradually earn their respect through her intelligence and determination.
One idea could be Hermione using her intelligence to change the Slytherin house's reputation from within. She could start study groups that include students from all houses, gradually breaking down the traditional rivalries. Another plot could involve her befriending some of the more misunderstood Slytherin students and together they work on a secret project that benefits the whole school.