Obviously, Harry is one of the main characters. And depending on how the fanfic is written, there could be some characters from the Forks world that are also main characters, like Bella or Edward if it's a crossover type of fanfic. There might also be some original characters created specifically for this fanfic to interact with Harry.
It would probably be a really interesting mix of two very different universes. The female Harry Potter would bring her magic skills to Forks. Maybe she'd use magic to deal with the gloomy weather or the strange things that happen in Forks. She could also interact with the characters from Twilight in unique ways, like using magic to help Bella with her vampire - werewolf drama.
One possible interesting plot point could be how Harry adjusts to the new environment in Forks. Maybe he has to deal with the gloomy weather which is quite different from what he's used to. Another could be his interactions with the local characters from the Forks setting. He might form new friendships or rivalries.
Well, he'd probably be really confused at first. I mean, Hogwarts is all about magic and Forks High School is a normal Muggle school. He might accidentally use magic when he's frustrated with a difficult class like Potions... I mean, Chemistry. And he'd surely stand out with his lightning - shaped scar.
Well, perhaps Harry Potter would arrive in Forks and be really confused by the small-town vibe compared to the wizarding world. He might meet the Cullens from Twilight and there could be some sort of misunderstanding at first. Maybe he tries to use magic secretly but it causes some strange happenings in the town.
Well, perhaps Harry could be a wizard - creature hybrid. In Forks, he might discover that the vampires there have a connection to the magical world he comes from. Maybe he uses his magic to help the Cullens with some sort of threat that normal vampire powers can't handle.
In the fanfiction, if Harry Vampire goes to Forks, he could potentially fall in love with a human there, just like Edward did in the original Twilight story. But his vampire nature might make things more complicated. He could have to struggle between his love for the human and his vampire instincts. Also, he might face challenges from the local vampire community if they don't accept an outsider like him.
Obviously, Harry Potter would be one of the main characters. And then there could be characters from Twilight like Bella Swan and Edward Cullen. Hermione and Ron might also show up to visit Harry in Forks, adding more wizarding elements to the story.
He'll most likely meet Bella Swan. Maybe he stumbles upon her in the forest and she's initially very wary of him, but then they start to talk and find they have some similarities in terms of being outsiders in their own worlds. He could also meet the Cullens. Edward might be intrigued by Harry's magic and Harry could be fascinated by Edward's vampire abilities.
Another theme is friendship and new relationships. In these fanfictions, she often forms new bonds with the characters in Forks. For example, she might become friends with Bella or the Cullens. And there could be a romantic sub - plot as well, like falling in love with one of the Twilight characters. The exploration of identity is also a big theme. She has to figure out who she is in this new place, while still being the female version of Harry Potter with her own set of magical skills and experiences.