A message posted to her Facebook profile says, "It is with a heavy heart that we share with all of you that Talia has earned her wings at 11:22am. Please lift her beautiful soul, her beautiful light to heaven."
Talia was first diagnosed with stage four neuroblastoma cancer on Valentine's Day in 2007 when she was just seven years old. The tumor develops from nerve tissue in infants and children.
After chemotherapy, surgery and radiation she was cancer-free for one year, but in September 2008 doctors discovered that the disease had spread to a lymph node near her heart.
Over the next four years she received various treatments, with the cancer spreading from one part of the body to the next.
She always said she didn't like wearing wigs because they made her feel fake, and that she began using makeup as a way to feel confident. Talia amassed more than 750,000 followers on her YouTube channel.
When her cancer spread to her bone marrow, doctors suggested the possibility of a marrow transplant, but Talia declined to go through with another operation and chose to enjoy her remaining days.
She eventually went on to appear on "The Ellen Degeneres Show" in October 2012 where Ellen revealed a portrait of Castellano as an honorary face of CoverGirl.
"You’re an old soul and you are very special and amazing, and I’m so honored that you wanted to meet me and that I got to meet you," Ellen said.
Ellen even tweeted about the news today, as did CoverGirl.
This year I met a very special girl, and today we lost her. Sending my heart to Talia's family. I'm so sad.— Ellen DeGeneres (@TheEllenShow) July 16, 2013
Talia Castellano was the meaning of a true COVERGIRL. Please join me in sending love and honoring her memory. pic.twitter.com/apfwOQRw8e— COVERGIRL (@COVERGIRL) July 16, 2013