Edward Cullen could be one of the main characters. He could be the one who finds the girl when she wakes up and tries to protect her from the dangers of the Twilight world, like other vampires who might want to harm her.
Alice Cullen could play a major role. Since she can see the future, she might foresee that the girl is important for some reason. So she takes the girl under her wing, helps her adapt to the vampire lifestyle in the Twilight world, and warns her of any impending dangers.
Perhaps she wakes up in a small town in Twilight. She soon discovers that she is being hunted by the Volturi because they think she has some special ability that could disrupt their order. She teams up with the Cullens to try and protect herself and figure out what's going on with her.
Edward would definitely be one of the main characters. His relationship with Bella, now a geisha, would be very interesting to explore. He might be both intrigued and a bit confused by this new side of her.
Maybe there's a mysterious visitor who comes to the ward from time to time. This person seems to know something about the girl's past or has some connection to her that she doesn't remember at first. As the story unfolds, this visitor becomes a key figure in the girl's life in the ward.
Often, the main character is an ordinary person who is suddenly thrust into the twilight world. They are usually confused at first, trying to make sense of their new surroundings. There might also be a wise old guide figure, like an ancient spirit of the twilight, who helps the main character navigate the strange world.
Her parents could be important characters. They might be the ones who made the decision to put her in suspended animation, either for her survival or for some other reason. Their relationship with her before and after the suspended animation could be a key part of the story.
Lefou could be an important character. He was Gaston's sidekick before, and now he has to deal with this changed Gaston. He might be confused at first but then could be one of the few people who stand by Gaston through the transformation, adding a layer of loyalty and friendship to the story.
A love interest who breaks the girl's heart can also be a main character. His actions, like cheating on her or suddenly leaving her without an explanation, can be the catalyst for her transformation into an evil character. Then the story could revolve around her trying to get back at him in devious ways.
There could be a kind - hearted old woman who takes the girl under her wing. She doesn't care about the dirty shirt and sees the potential in the girl.
There could be a best friend of Gray who starts to suspect that Gray is not what she seems. This friend could play a crucial role in helping Gray either keep her secret or come to terms with revealing it.
One of the main characters could be Shiro. Shiro has always been like a big brother to Keith. So when Keith turns into a girl, Shiro would be there to help him adjust. He'd make sure Keith is safe and comfortable in his new form. Also, Hunk could be a main character. Hunk would probably be the one to offer emotional support and cook some comfort food for Keith during this tough time of adjustment.