Well, it could be that the fanfiction is trying to show Ginny's jealousy or resentment in a new light. Perhaps she's jealous of Harry's fame or the attention he gets. Or maybe the writer is simply exploring a 'what if' scenario where Ginny and Harry's relationship took a different turn from the start. In the original story, they end up together, but fanfiction allows for alternative storylines, and this could be one of them where Ginny hates Harry for various reasons that might be related to their different personalities, goals or the pressure of the wizarding world around them.
One possible reason could be a creative twist by the author to explore different relationship dynamics. Maybe they want to create conflict and drama. For example, the author might make Harry misunderstand Ginny's actions or intentions, leading to this false sense of hatred in the fan - made story.
It could be that the fanfiction writer wants to create some sort of conflict. By having Harry's kids hate Ginny, it adds a new layer of drama to the story. They might be made to believe false things about Ginny which lead to their hatred.
One characteristic could be a complete deviation from the original story's relationship dynamic. It might also involve a lot of angst and conflict. For example, the fanfiction could focus on how Ginny is affected by Harry's hatred, and how she tries to deal with it.
Maybe the writer wants to create a unique plot twist. In some fanfics, authors like to deviate from the original relationship to explore different character dynamics.
It's probably not as popular as the more positive, canon - compliant fanfictions. Most fans like to see the characters in relationships that are in line with the original story, so this type of 'hate' fanfiction might have a niche audience.
One consequence could be a split in the friendship group. If Harry hates Ginny, Ron, being Ginny's brother, would be in a difficult position. It could lead to a divide between Harry and Ron as well.
This type of fanfiction can also change the character interactions. Friends of Harry and Ginny may be forced to take sides or try to reconcile them. For instance, Hermione might be in the middle, trying to figure out what went wrong and how to fix it. It can make the story more about relationship drama rather than the typical Harry Potter adventures against dark forces.
Harry could also be very hurt. He might start to question what he did wrong and try to talk to Ginny to find out the reason. He might say things like 'Ginny, I don't understand. What have I done?' in an attempt to clear up the situation.
Some fans might be really put off by this concept as they love the idea of a harmonious family in the Potterverse. It could create a divide among fans, with some who enjoy the new and edgy take of the fanfiction and others who think it goes against the spirit of the original series.