(NEW YORK) -- Wayne and Lori Earl receive messages every day from strangers still mourning their late daughter, Esther. Esther's YouTube videos and blogs still receive comments of "I love you" from people discovering her for the first time. Bloggers from all over the world mention her in posts in various languages.
It's been more than two years since Esther died at the age of 16 after a four-year battle with thyroid cancer, but it's possible that more people celebrate and mourn her now than ever before.
"She reminded me that while we imagine sick people as 'fundamentally other,' they are not," said author John Green, who met Esther at a Harry Potter convention, became her friend and dedicated his most recent novel, The Fault in Our Stars, to her last January. "They are every bit as alive as any other human being."
Since her death, Esther has inspired two books, a charity organization, an unofficial holiday and countless online communities she loved to participate in when she was home from school and feeling isolated because of her illness.
Esther's diagnosis, metastasized papillary thyroid cancer, came on Thanksgiving Day 2006. She already had tumors in her lungs. Although the Earl family had recently moved to France, which had been a dream of Wayne and Lori's, they moved back to the United States in early 2007 to be near Boston Children's Hospital for Esther's treatment.
The following Thanksgiving, in 2007, her team of doctors told the Earls that Esther was terminal. All treatment would go toward prolonging her life, not curing her of cancer.
Over the next three years, Esther would undergo tests, surgeries and experimental chemo and hope for another year.
Through it all, she couldn't often go to school, but she loved to read. She soon found that she could be "normal" online through blogs and videos.
An avid Harry Potter fan, Esther learned about Green's books and joined his online community called the Nerdfighters. She also connected with Andrew Slack, who founded the Harry Potter Alliance as a way to blend fandom with activism.
Esther and Green met in 2009 at LeakyCon, the Harry Potter conference, during the concert part of the event when everyone is supposed to dance. Green was feeling awkward and noticed Esther sitting at a table off to the side, so he went over to say hello.
"The birth of our friendship was that I don't like to dance, and Esther was too sick to dance," Green said. "I liked Esther a lot immediately. ... She was just a nice, normal person. Uncommonly mature. Uncommonly empathetic. She sensed my own anxiety in those situations."
He didn't even realize she was a key organizer in his Nerdfighter fan community but eventually they became friends despite the more than 15-year age difference.
The month before she died, Esther invited Green to her Make-A-Wish in Massachusetts. The Make-A-Wish Foundation grants terminally ill children wishes -- for example, to play football with the Eagles or meet Cookie Monster -- but Esther just wanted to meet her online friends in person.
After that, Green posted a video about Esther, and people wanted to know more about her. He told his viewers to vote for the Harry Potter Alliance, which was competing for funds at the time, with Esther -- but not for Esther, "because if I say that to Esther she will throw up in the back of her mouth and hate me."
Although Green originally told the world about Esther by video-blogging about her and later dedicating his best-selling novel to her, Slack said he believes Esther gained a following because of her "quirky" and "absurd" sense of humor and her ability to listen to others.
"John Green loves Esther because Esther was lovable," Slack said in an email. "And that's why I love Esther."
Esther's 16th birthday became Esther Day, and Green told her it could be about whatever she wanted. She said it would be about family, and telling people you love that you love them -- kind of a reverse Valentine's Day. Three Esther Days later, the Nerdfighter community still celebrates it. It even had a celebration in Quincy, Mass., this year.
Esther died in the early hours of Aug. 25, 2010, three weeks after her 16th birthday and two days after she decided to withdraw from high school to get her GED.
Copyright 2012 ABC News Radio