One possible storyline could be that Harry leaves Ginny due to some external threat that he doesn't want to endanger her and the unborn child. For example, he might have discovered a new dark wizard on the rise and decides to go into hiding alone to draw the danger away from his family.
She might also be sad and heartbroken. Ginny is a strong character, but being left alone while pregnant is a huge blow. She could withdraw from her friends and family for a while as she tries to come to terms with the situation and figure out how to raise the child on her own.
Ginny's character could develop in several ways. She may initially be heartbroken and feel lost without Harry. But as the pregnancy progresses, she could find an inner strength. She might become more protective, not just of her unborn child but also of her own feelings. She could also become more empathetic towards other single mothers in the wizarding world. This experience could make her a more complex and well - rounded character, no longer just the girl who was in love with Harry but a strong woman facing a difficult situation.
In the fanfic, their relationship could develop gradually. Harry might be hesitant at first due to his past experiences with Cho. However, Ginny's warmth and understanding draw him in. They might start off as friends, sharing secrets and having deep conversations. As time passes, they realize their feelings are more than just friendship and start a romantic relationship. Ginny's family also plays a role, as the Weasleys welcome Harry, which makes him feel more at home and closer to Ginny.
Well, in this kind of fanfiction, a plot development could be that Ginny, being pregnant, discovers new magical abilities or powers related to motherhood. This could be a unique take on the story. Also, the wizarding community might react in different ways to Ginny's situation. Some could be supportive, while others might shun her because of Harry's departure. It could lead to Ginny having to fight for her place in the community and prove that she can be a great mother on her own terms.
Obviously, Harry would be an important character even though he leaves. His actions before leaving and potential return would greatly affect the story. Also, the Weasley family, especially Ginny's mother Molly. Molly would probably be very involved, offering her motherly advice and support. Ron and Hermione might also be involved. Ron as Ginny's brother would surely have an opinion and Hermione could be there for Ginny as a friend.
One possible plotline could be Ginny leaving Harry due to the pressure of his fame. She might feel overshadowed and decides to pursue her own life away from the spotlight. Another could be a misunderstanding. Maybe she misinterprets Harry's actions or words and in a fit of anger, leaves him. Or perhaps an external threat forces her to leave to protect Harry, like a dark wizard threatening her to stay away from him so as not to be used against Harry.
In this fanfiction, Ginny might find strength within herself that she didn't know she had. She could start to form new relationships with other characters who help her through the pregnancy. For example, she could become closer to Hermione, who could offer practical and emotional support. The pregnancy could also be a catalyst for changes in the wizarding society's view on single motherhood. It could lead to new laws or social norms being established, and Ginny could be at the forefront of this change.
Ginny herself might be conflicted. Even though she made the decision to leave, she would still have feelings for Harry. She could be sad and second - guess her decision. The Weasley family would be divided in their reactions. Molly would be worried about both Ginny and Harry, trying to patch things up. Arthur might be more understanding of Ginny's need for independence but would also hope for a reconciliation. Ginny's brothers would have different reactions. Some might side with Ginny, while others might think she was too hasty in leaving Harry.
One possible reason could be that Harry realizes he has stronger emotional and intellectual compatibility with Ginny. He might find that Ginny understands his complex life as a wizard better, especially with her own experiences in the wizarding world. Also, Ginny is more in tune with Harry's adventurous spirit, which Cho might not be as much.