I'm not sure who Amelia and Eleanor are in this story without reading it. They could be friends, sisters, or just two people who happen to go on a ride together.
Eleanor and Park isn't historical fiction. It focuses on the present-day experiences and relationships of the main characters, without delving into historical events or periods.
At the beginning, Eleanor is a rigid character with set routines. As the story unfolds, her relationship with Raymond and her own experiences gradually break down her walls. She begins to face her past traumas and in doing so, becomes more confident and self - aware. For instance, she starts to take better care of her appearance and interact more with people in a positive way. This development is slow but steady throughout the novel.
It's hard to say for sure. If it's presented as a made-up tale or lacks real-life references, it's likely fiction. But without more details, it's difficult to determine conclusively.