Yes, there could be. Some fanfic writers might be interested in exploring alternative relationship dynamics just for the sake of creative storytelling. But it's not in line with the general perception of the characters in the official story. They may rewrite the characters' personalities a bit to make such a plot work in a non - inappropriate way.
I'm not sure specifically if there is a fanfiction titled exactly like that, but in the Harry Potter fanfiction community, all kinds of relationship - based plot twists are explored. It could be that someone has written a story where Cho cheats on Harry. You can try searching on popular fanfiction websites like Archive of Our Own or FanFiction.net to find out.
Often, there could be a theme of self - discovery. Maybe Harry, through this wrong action, starts to realize things about himself that he hadn't before. Also, the theme of forgiveness might be present. Ginny would have to decide whether to forgive Harry, and Cho might have to deal with the consequences of being involved in such a situation. And then there's the theme of how the wizarding community views such behavior, which could be explored in terms of its social norms.
Friendship is another theme. Stories often show how Ginny and Cho can overcome their initial rivalry and become friends. For example, they might bond over their shared experiences in the wizarding world or their mutual care for Harry in a more platonic way. This theme helps to add depth to their characters.
Ginny might initially be heartbroken. She could retreat into herself, feeling betrayed and confused. In some fanfictions, she may cut off all contact with Harry immediately.
One reason could be that Cho is still hung up on Cedric. Even though she starts dating Harry, her feelings for Cedric might resurface and lead her to cheat. Another possibility is that she feels pressured in her relationship with Harry due to all the attention they get at Hogwarts and looks for an escape with someone else.
This is a very controversial and uncanonical concept for the 'Harry Potter' series. While there might be some fanfiction out there exploring such dark and untrue-to - the - original - story ideas, it goes against the essence of the relationships J.K. Rowling created. I personally don't support such fanfictions as they distort the well - loved characters and their relationships.
One possible reason could be miscommunication. Maybe Ginny feels neglected by Harry because he's so caught up in his own heroic deeds and doesn't pay enough attention to her. So she might seek comfort or excitement elsewhere.
She could also be very hurt and go into a state of deep sadness. She might isolate herself from Harry and their mutual friends for a while. Ginny would likely question her own self - worth and wonder what she did wrong in the relationship. But as time passes, she might find the strength to move on and focus on her own life, like her career or other relationships.
In this type of fanfiction, it could be that Harry has some unresolved issues from his past relationship with Cho. He sees Ginny as a distraction from dealing with those. But as time goes on, he can't ignore the pull he still feels towards Cho. He may leave Ginny when he realizes that he can't move forward in his life without exploring what could have been with Cho again.