There could be some underlying mental health issues within the family. Perhaps her parents have some undiagnosed conditions that make them more prone to lashing out. In the fanfiction world, this could be explored further, like how Hermione tries to understand and deal with this aspect of her family situation while also dealing with the abuse.
In the fanfiction, it could be related to family values. Draco comes from a family with certain beliefs about blood purity. Hermione being a Muggle - born might be seen as beneath him by his family's standards. So, Draco might abuse Hermione as a way to show his superiority based on those wrong family - instilled ideas.
Well, in some fanfictions, it could be that they're under the influence of some dark magic or a spell that makes them turn against Hermione. Or perhaps they're misinformed about her actions at Hogwarts and think she's a bad influence. Also, some writers might use it as a plot device to create a rift and then build a story around Hermione trying to fix things with her parents.
One possible reason could be her involvement in the wizarding world. If her parents are muggles and they find out about the extreme dangers she faces in the magical realm, they might disown her out of fear for her safety. Another reason could be if she starts to show more loyalty to the wizarding community than to her muggle family, making them feel like she no longer belongs with them.
Perhaps in this fanfiction, her parents have some secrets that Hermione discovers. These secrets could be related to the wizarding world and their connection to it. Their attempts to hide these things from her make her feel betrayed and thus lead to her hatred. For instance, if they knew about some dark magic in their family history but kept it from her.
One possible reason could be social class differences. Hermione's parents are Muggles and might view Ron's large, wizarding family with some prejudice. They may see the Weasleys as a bit chaotic and irresponsible because of their financial situation.
Perhaps some writers are trying to explore extreme scenarios to show the character's resilience. But this is a very wrong approach as it involves abuse. It could also be that the fanfiction community has not been strict enough in policing such content, leading to some writers thinking it's okay to write such things. In a proper fanfiction environment, characters should be respected and not subjected to such inappropriate abuse.
Draco's father, Lucius, might be very disdainful at first. He has a strong sense of pure - blood superiority and Hermione is a Muggle - born. His mother, Narcissa, might be more reserved in her dislike. She could be more focused on how Hermione's presence affects Draco.
One possible reason could be that they are too involved in their own shinobi duties. The world of ninjas is full of dangerous missions, and they might be constantly away on important tasks, leaving Naruto feeling neglected.
One possible reason could be a disagreement over how Molly treats Harry. Maybe Molly is being overprotective of Harry in a way that Hermione thinks is hindering Harry's growth as a wizard. For example, if Molly tries to stop Harry from taking certain risks that Hermione believes are necessary for his development.
Another reason could be a rift in their friendship caused by outside factors. For instance, if the wizarding community starts to turn against Harry because of false rumors or misinformation, Hermione might find it too difficult to stand by him. She may fear for her own reputation or safety, and this could lead to her abandoning Harry.