It could be that there are some rumors going around. In the wizarding world, rumors spread like wildfire. If someone saw Harry in a compromising situation with another person, even if it was innocent, and told Draco, he might believe it without asking Harry for his side of the story. Also, if Harry has been secretive about some of his activities lately, it could fuel Draco's suspicions.
Perhaps Draco tries to win Hermione back even though he thinks she's cheating. He could do things like buying her gifts or doing favors for her, all while being angry and hurt inside. This would create a very complex emotional situation for both characters.
In many fanfics, misunderstandings like this can drive the plot. Maybe Draco saw Hermione spending a lot of time with another character and jumped to conclusions. It could be she was just working on a project or helping a friend.
Harry can start by being completely honest with Draco. He should sit down with Draco and tell him about all his recent activities, who he has been with, and why. For example, if he has been working on a project with a classmate, he can explain the details of the project.
In some fanfiction, this could happen due to a power play. Maybe Draco's family still has some influence and he uses it to force Harry. It could also be a result of a misunderstanding or a dark plot twist where Draco believes he has no other choice to get what he wants.
Another possibility is that the writer wanted to explore different character reactions. Naruto might initially be devastated. He could go through a phase of disbelief and then anger. However, if it's a well - written fanfic, there would likely be a resolution where the truth comes out and their relationship is either repaired or redefined.
One possible reason in such a fanfiction could be a magical bond that forms between Harry and Draco unexpectedly. This bond might be stronger than his relationship with Ginny. It could be a result of a shared magical experience or a prophecy that ties them together in a way that makes Harry question his feelings for Ginny and ultimately choose Draco.
Well, it could mean that Draco misjudges Harry. Maybe he sees Harry with a doll once and jumps to the conclusion. This could lead to some interesting interactions. For example, Draco might tease Harry about it, which could either cause a fight or, in a strange way, bring them closer as they start to understand each other better through this misunderstanding.
She might directly ask him about her suspicions. Just come out and say 'Harry, I think you're cheating on me. I've noticed you acting strange lately.'
Harry might be confused at first. He doesn't understand why Draco would think he's a doll fan. So he might just shrug it off and not pay much attention, thinking Draco is just being his usual difficult self.
In the fanfiction world, miscommunication often plays a big role. Perhaps Harry was involved in some secret mission or task that he couldn't tell Ginny about right away. But Ginny, not knowing the real situation, might misinterpret his secrecy as cheating. For instance, he might be sneaking around to protect Ginny from a potential threat, but she doesn't see it that way.