A more character - centric plot could be about Rosalie and Bella finally coming to a true understanding and friendship. Alice could be the catalyst in this, arranging situations where they have to work together and learn about each other's pasts. This could include Rosalie sharing her human life story with Bella, and Bella sharing her fears and hopes for her new vampire life.
One plot idea could be a story where Bella, Rosalie, and Alice have to work together to solve a mystery in the vampire world. Maybe there's a new threat that only their combined skills can handle. Another could be a story focused on their friendship, like a road trip where they discover new things about each other and themselves. Or perhaps a story where they use their powers to help humans in a small town without revealing their true nature.
A third plot might involve a mystery in the modeling world. Bella, Alice and Rosalie are models, and suddenly, there are strange disappearances of models from their agency. They decide to investigate. As they dig deeper, they find that there is a jealous rival trying to sabotage their agency. They use their different skills - Bella's tenacity, Alice's intuition and Rosalie's beauty and charm - to expose the culprit and save their agency.
One idea could be that Bella and Rosalie have to team up to protect the Cullen family from a new vampire threat. They start off disliking each other but as they face challenges together, they develop a mutual respect.
One plot idea could be that Rosalie and Bella discover a hidden power within their futa forms that is connected to the supernatural world around them. They then have to navigate how to use this power while also dealing with the reactions of their friends and family in the Twilight universe.
One possible storyline could be their adventures together in the vampire world. They might face challenges from other vampire clans and have to use their combined powers to overcome them.
Maybe a plot where they form a band in the fanfiction world. Alice with her elegance, Rosalie with her confidence, and Bella with her charm could create a really cool and unique musical group, performing in different places and attracting all kinds of fans.
Perhaps they embark on a journey to discover more about their own origins. This could involve traveling to different places, meeting old vampires who might know something about their past. Along the way, they learn more about each other and grow closer as sisters.
One idea could be that Bella discovers Rosalie's possessive nature towards her new vampire life. Rosalie might try to control Bella's actions to prevent her from making what she sees as mistakes. For example, Rosalie could be possessive over the 'right' way to be a vampire and try to keep Bella from straying from it.
One great 'Alice Rosalie and Bella fanfiction' could be one where they go on a road trip together. It would be interesting to see their different personalities interact during the journey, like Alice's premonitions causing some unexpected detours and Rosalie's protective nature coming out when they face any sort of danger. Bella, of course, would be in the middle, trying to understand their complex relationship.
One possibility could be that they form a strong bond like a family. They support each other in the challenges they face in the vampire world. For example, they might work together to protect their territory from other vampires. They could also share their different experiences and knowledge, like Alice's visions helping them prepare for future events.