There could be other vampire clans that see the Cullens' camping trip with Bella as a threat or an opportunity. They might try to disrupt their time in the woods. Another possibility is that some shape - shifters in the area don't like the presence of vampires and decide to cause trouble.
Well, they might encounter some unique supernatural creatures in the woods. Since the Cullens are vampires, there could be other dangerous beings that are attracted to their presence. Maybe they'll have to protect Bella from these threats.
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.
It could be another vampire clan. Maybe they are jealous of the Cullens' interest in Bella or they think that Bella's presence among the Cullens will disrupt the balance of power among vampires. So they try to get Bella from the Cullens, making them the main antagonists.
Her father, Charlie, might try to rescue her. He loves Bella deeply and would be very worried when she goes missing. He could start investigating and find out that the Cullens are involved.