Final answer:
Ivy is likely experiencing cryptoamnesia, a psychological phenomenon where an individual unintentionally plagiarizes unseen material, believing the idea to be their original work.
Step-by-step explanation:
In Ivy's case, she could likely have experienced something known as cryptoamnesia. This is a psychological phenomenon where an individual unintentionally plagiarizes someone else's work by forgetting about the source and believing the idea to be their own. In other words, Ivy unconsciously copies the narrative of a short story she previously read and genuinely believes that the narrative is her original creation. This is more prone to occur if she had exposure to the original work (the published writer's short story) a while ago, in this scenario, during her freshman year in high school, leading to memory gaps and difficulty in differentiating between read sources and personal thoughts.
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