For years, its origin was a mystery. Was it a trollfic, or was it really written by a semi-illiterate teenager? The mystery came to a head recently when drama blew up over a Young Adult Novel that bought its way to the Number One spot on the bestsellers list. (Info on that here http://ew.com/books/2017/08/25/handbook-for-mortals-how-nyt-best-seller-list-works/) A rumor began that the author of this book had also written My Immortal, but this was quickly debunked when Rose Christo (real name Terry Christo) revealed herself as the real author.
This came with the announcement that she would be writing a memoir on the true story of My Immortal. (https://www.amazon.com/Under-Same-Stars-Rose-Christo/dp/1250147034) Which she claims is that she wrote it to find her long lost brother while in foster care. Sounds far-fetched, right? That's because it is.
Her brother happens to be a member of this very forum (@DawnDusk ), and his side of the story paints a different picture, not that she lost communication with him while being shuffled through the system, but that she just doesn't contact him and never was in foster care. He began poking holes in her claims in this thread; https://kiwifarms.net/threads/author-of-my-immortal-possibly-found.33996/
On her Tumblr, she also frequently blogs about the struggle of being Native American/Indian. Problem with that is she's actually white.
Whether My Immortal itself was genuine or not, these lies show that its author is worthy of further discussion.
2021 Update: With the thread unlocked for now, I’m taking the opportunity to say here in the OP that Rose is most likely NOT the author of My Immortal, if you are here due to interest in the fic’s origin, Rose is not the answer. When I initially made this thread, I was under the impression that she may have been the author, however as more and more lies were revealed and her “proof” of authorship was shown to be very flimsy, I no longer think her claim of having written My Immortal holds any water.
Rose Christo seems to be a pathological liar that was untruthful about every aspect of her life, and there is no evidence to show she suddenly told the truth about the fanfic, and instead was using it as a springboard for other lies.