I'm not sure. It depends on how it's presented and what the creators claim. Sometimes movies or books labeled as such might have elements of truth mixed with fiction.
The Forgiven (2022) is purely fictional. It was written to engage and captivate the audience through imaginative storytelling rather than being based on real events.
Since I don't know the exact content of 'the forgiven novel', it might be about the process of forgiving. It could tell the story of characters who have to face and overcome grudges, either in a family context, among friends, or in a larger community. Maybe it shows how forgiveness can transform people and their relationships.
As I haven't had the chance to read 'the forgiven novel', it's hard to say. But often in novels about forgiveness, there would be a character who has done something wrong and another who has the power to forgive. There could also be supporting characters who influence the main characters' decisions regarding forgiveness, like friends or family members who give advice or create more conflict around the issue.
Yes, there are likely fanfictions with such a plot. The Harry Potter fandom is vast and diverse, and writers explore all kinds of relationship dynamics. However, it might not be a very common or mainstream take on the characters' relationships.