Perhaps there's some external influence on Ginny. Maybe a dark magic spell was cast on her that made her have negative emotions towards Harry. In the wizarding world, there are many powerful spells that can manipulate emotions, and if Ginny was under the effect of such a spell, it could lead to her saying she hates Harry.
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.
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 plotline could be that Ginny accidentally hurts Harry during a Quidditch match. Maybe she's trying to catch the Snitch and doesn't see Harry in her way, and her broom collides with his, causing him some physical pain. Another could be an argument where Ginny says some harsh words that emotionally hurt Harry. For example, if she's jealous of his friendship with Hermione and lashes out at him, saying things like he doesn't really care about her as much as he does Hermione.
One possible reason could be that the 'light' in the fanfiction represents something he associates with strict rules or a false sense of goodness. Maybe it has been used to manipulate people, and Harry, being perceptive, sees through it and thus hates it.
One possible reason could be that in the fanfiction, her parents might have made a sacrifice that left her alone, and she resents them for not being there for her. Maybe she feels abandoned and that has led to her hatred.
One possible reason could be a growing apart due to their different career paths. Harry, being deeply involved in the wizarding world's security and Ginny having her own Quidditch career. Another reason might be the stress of living in the public eye. Their relationship may not be able to withstand the constant scrutiny and pressure from the wizarding community.
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 possible reason could be a misunderstanding. Maybe Harry was wrongly accused of something, and Ginny's temper got the better of her. For example, if there were false rumors about Harry being unfaithful in the fanfiction world.
In this fanfiction, perhaps there's some miscommunication. Maybe the Weasleys' boisterous nature is misconstrued by Harry. For example, their large family dynamic might be overwhelming to him at times, which could be a reason for the 'hate' in the fanfic.