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.
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.
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.
Another character could be Blaise Zabini. He is also from a pureblood family. Fanfictions might pair him with Hermione as they explore the pureblood culture together. He could introduce Hermione to different aspects of pureblood society, and they might develop a friendship or something more as they interact.
Hermione is surely a main character. In addition, there could be some older pureblood wizards or witches who serve as her mentors in this fanfiction. For instance, Narcissa Malfoy might be involved. She has her own complex character and her knowledge of the pureblood ways could be passed on to Hermione. And of course, Harry and Ron might also make appearances, showing their reactions to Hermione's new adventure in the pureblood training.
One of the main characters they would interact with is Harry. Harry is Hermione's best friend, and he would surely have an opinion on her marriage to Remus. He might be initially worried about Hermione but then see how well they get along. Another character could be Sirius. Since Sirius is Remus's friend, he would be involved in their relationship. He could offer advice to Remus or be a bit skeptical about Hermione at first. Also, Dumbledore might interact with them. He often has a hand in important matters in the wizarding world and could either support or have some concerns about their marriage under the new law.
Obviously, Hermione and Harry are the main characters. They are the central focus as they deal with the Pureblood Society.
Well, Ron is a given. He's Hermione's significant other, so he'd be deeply involved in the whole process. Luna Lovegood might also make an appearance. She has an unique perspective and could bring some calmness and different kind of support. And don't forget about Hagrid. He has a big heart and might come to offer his congratulations and well - wishes in his own, endearing way.
Some Slytherins might oppose her. They are often traditionalists and may not like her new - fangled ideas for the school. For example, Draco Malfoy could be one of the opponents as he has had a long - standing rivalry with Hermione.
Other characters like Ginny Weasley could be part of 'hermione fails' fanfiction. Ginny might be Hermione's confidante when she fails in a relationship, offering advice based on her own experiences. Neville Longbottom could also be involved. He could be in a situation where Hermione fails to recognize his potential or she fails to help him when he needs it most. And of course, the Weasley twins, Fred and George, could be involved. They might use Hermione's failure as inspiration for one of their pranks or they could be the ones to cheer her up in a humorous way after she fails something important.
Harry and Ron are likely to be main characters. They would probably be intrigued by Hermione's new Jedi abilities and might get involved in her adventures. Maybe they try to learn some Jedi skills from her too. Another character could be Dumbledore. He would be curious about this new form of power Hermione has and might offer his wisdom and guidance.