It's possible that the Volturi would initially be curious. They are an ancient group, and Greek mythology has its own ancient roots. They might wonder why Bella is attracted to it. But if her interest starts to influence the vampire community around her, for example, if other vampires start to get interested in human fanfiction because of her, they would likely put a stop to it as it goes against their traditional and rather rigid ways.
They might be indifferent. After all, they have more important vampire - related matters to deal with. Bella's interest in Greek god fanfiction may be just a minor and strange human hobby to them.
The Volturi could view it as a form of rebellion in a way. They are used to having control over everything in the vampire world. Bella's fascination with something outside of their realm might be seen as her not fully conforming to their idea of what a human involved with vampires should be like. So they might try to suppress it in some way.
If the Volturi find out Bella is into Greek god fanfiction, it could have a range of reactions. They are a rather old - fashioned and strict group. On one hand, they might simply dismiss it as a harmless human quirk. But on the other hand, if they think it somehow affects Bella's loyalty to the vampire world or her relationship with Edward, they could take a more serious stance. For example, if they believe her interest in Greek gods makes her question the power structure in the vampire world, which is centered around them, they might try to discourage her or even take more extreme measures to keep her in line.
They would probably be very critical. The Volturi are all about maintaining the status quo in the vampire world as they see it in the Twilight series.
The Avengers would react very strongly. Steve would be the first to offer moral support. He'd tell Peter that being bullied doesn't define him. Natasha would start investigating who the bullies are and their motives. And Vision, with his unique perspective, would try to help Peter see the situation from a different angle, to understand that the bullies are often the ones with insecurities. Meanwhile, Sam would be there to cheer Peter up with his friendly banter.
Zeus would probably be furious. In the God of War series, he is often depicted as a cruel and power - hungry god, which is a far cry from his traditional role as the king of the gods. Fanfiction might exacerbate this negative image, and he would not take kindly to it.
Some fans might be very shocked as it goes against the traditional relationship perception in the original series. They would find it disturbing because of the father - daughter - like relationship they had in the source material.
The Cullen family members will have different reactions. Carlisle, as the patriarch, would be diplomatic. He would try to smooth things over and show that the Cullens are following the rules. Alice might be using her gift to foresee any potential danger during the visit. Emmett, on the other hand, would be more ready for a fight if it came to that. As for the Volturi, they would come in with an air of authority, and their members like Aro would be observing every little detail of the Cullens.
In the Twilight universe where this fanfiction is based, the Volturi kings are Aro, Caius, and Marcus. They are the leaders of the Volturi, an ancient and powerful coven of vampires.
Bella Swan's character could be developed by having her explore different aspects of herself. In the context of Greek gods, she might discover a more passionate side of herself, like the passion associated with the Greek concept of eros. This could make her more confident and change her relationships. She could also be developed through her experiences with the Greek gods' powers. If she gets a taste of Athena's wisdom, she could use it to solve problems in Forks that she couldn't before. This would make her a more respected and important figure, not just among the Twilight characters but also among the Greek gods she encounters.
Bella would be heartbroken. She has put so much trust in Edward, and this act of cheating would make her question everything. She might become angry and lash out at both Edward and Tanya. She could also become very sad and isolate herself from others.
One common theme is identity. Bella has to figure out who she is in this new role as a Greek - god - like figure. For example, in many stories, she may struggle with the powers she suddenly has and how they change her sense of self.