Well, in some fanfictions, it often starts with Draco using a spell or a potion on Harry. Then, Harry has to deal with the sudden change. He might struggle with his new identity at first. For example, he could be confused about how to act as a girl in the wizarding world. There could be a lot of humorous situations, like when he tries on girl's robes for the first time and doesn't know how to walk in them properly. Also, his friends might have different reactions. Hermione could be more empathetic and try to help him adjust, while Ron might be completely bewildered.
A possible fanfiction plot could be that Draco, now a girl, discovers new magical abilities that were suppressed in his male form. These powers could be related to a more intuitive connection with magic, something that is often associated with femininity in the wizarding world. This newfound power could put her in a position where she has to choose between using it for the benefit of Slytherin or for the greater good of Hogwarts, creating a moral dilemma for her character.
As for the teachers, Dumbledore would be calm and try to understand the situation. He might see it as an opportunity for Harry to learn something new about himself and magic. Snape, on the other hand, might be sarcastic and critical, blaming Harry for getting into such a situation, but secretly he might also be intrigued by the magic used.
Maybe Draco is jealous of Harry's popularity and power. Turning him into a vampire could be a way to strip him of his status among the wizarding community. Vampires are often feared and shunned, so Draco might think this would be a good way to get back at Harry.
When it comes to Draco's relationship with Harry Potter and his friends, things could get really interesting. Harry might initially be shocked but could also feel a sense of pity. Hermione could be more sympathetic and might try to help Draco adjust, which could lead to an unlikely friendship. Ron, on the other hand, would probably be the most skeptical and might take a long time to accept this new Draco.
His personality might become more empathetic. As a girl, Draco could start to see things from a different perspective. For example, he might be more sensitive to the way others are treated, especially other girls in Hogwarts.
In terms of his relationships with his Slytherin peers, some might look down on him. But others could be intrigued. Pansy Parkinson, for example, might see Draco as a girl as a threat to her status as the 'queen bee' in Slytherin. However, some of the more open - minded Slytherins could befriend Draco and help her deal with the challenges of being a girl in a very traditional and often misogynistic wizarding society.
Perhaps the plot could involve Petunia having some sort of magical awakening or discovery that leads her to perform this transformation on Harry. In this fanfiction, Harry might then use her new female identity to infiltrate parts of the wizarding world that are more difficult for a male to access, like certain all - female magical groups. And this could lead to all sorts of adventures and revelations about the wizarding world's gender dynamics.
Another possibility is that it's an accidental result of a powerful magic clash between Voldemort and Harry. When their magic collides in a certain way, it causes an unexpected transformation on Harry, turning him into a girl. This would add a whole new layer of complexity to their relationship and the overall story.
Another aspect of her character development could be in her appearance and how she uses it. As a female, she might initially be self - conscious about her new look, but then learn to use her beauty or femininity as a tool. She could charm people in different ways, either to get what she wants or to protect herself. However, she would also have to be careful not to lose her true self in the process, and this struggle could be a major part of her character arc in the fanfiction.