They might be quite amused. Bella could find it interesting to see different takes on her relationship with Edward during that difficult time in New Moon. The Cullens, especially the more light - hearted ones like Emmett, might get a good laugh out of some of the wilder interpretations in the fanfiction.
Well, Carlisle would probably be very diplomatic about it. He might see it as a creative expression of the fans' love for their story. Esme, on the other hand, could be a bit more emotional and find it endearing how fans have delved into their world. And the younger Cullens like Alice might enjoy seeing the different scenarios and twists that the fanfiction writers come up with.
They would probably have a lot to talk about. Bella might share with Edward the parts that she found either really accurate or really off - base. The Cullens might discuss among themselves how the fanfiction portrays their family dynamics, especially things like their relationships with each other and with Bella.
Some of them might see themselves in a new light. For instance, if there are fanfictions that portray Jasper in a different way, he might start to think about his own character more deeply.
She might start by giving them the silent treatment. Just ignoring them completely when they try to talk to her, which would be a very human way of showing anger.
Well, it could be due to the way the Cullens interact with the other people in Forks. If Bella notices that they are being manipulative or using their powers in a way that she doesn't like to influence the townspeople, that could make her start to hate them. Also, if there is some kind of power struggle within the Cullen family that starts to affect Bella negatively, like she gets caught in the middle of it or she sees how it's causing harm to those she cares about, she might turn against them.
It could be that the fanfiction writer took a different approach to the story. In some fanfictions, the Cullens could be involved in situations that go against what Bella stands for. Perhaps they are written to be more secretive and untrustworthy, leading to Bella's hatred.
I'm not sure specifically as there could be many different takes on it. Generally, it might be about Bella using her singing in a context related to the Cullen family in a fan - created story.
Yes, it is quite common. Fanfiction writers often use this scenario to explore the relationship between Bella and the Cullens. It gives an opportunity to show the Cullens' caring side towards Bella.
In some fanfictions, the Cullens might hate Bella because of jealousy. Maybe other vampires are jealous of the attention she gets from Edward. Another reason could be that she brings too much danger to their family. Her presence could attract unwanted attention from other vampires or vampire hunters, which puts the Cullens at risk.