Plagiarized or Prepublished

Jenny is determined to keep up her grades so she can enter an Ivy League school even though she's unable to attend classes because of her illness, but is she willing to cheat to do it? Proctor the school's new virtual assistant and plagiarism checker has flagged her final assignment as plagiarized from sources on the internet. When her teacher Martha informs her of this Jenny claims the work was a fan essay she'd wrote for a LitRPG fansite.
If this is true does this count as plagiarism or prepublishing? Jenny's scholastic career hangs on the answer to this question in this short story.