The Orlando, Fla., teenager became a YouTube sensation with her motivational makeup tutorial videos, which captured the attention of the TV host. Talia died Tuesday at Arnold Palmer Hospital, with the announcement coming from her official Facebook fan page.
"It is with a heavy heart that we share with all of you that Talia has earned her wings at 11:22am," the post read. "Please lift her beautiful soul, her beautiful light to heaven and please send your love and prayers to her family during this most difficult time. God speed little one, may you be free from pain and suffering, may your soul feel the light and love that you brought to so many of us on this Earth during the short time you were here with us. We will miss you more than you will ever know baby girl."
In 2007, Castellano was diagnosed with Stage 4 neuroblastoma, an aggressive cancer. She was 7. She underwent chemotherapy and went into remission for 13 months, but the cancer returned the next year. The cancer went in and out of remission for several years. In August 2012, her cancer spread to her bones, and she developed pre-leukemia.
However, during her bouts with the disease, after she lost her hair, the affectionately called "professional, YouTube Makeup Guru" refused to don a wig. Instead, she chose to boost her self-confidence by experimenting with makeup at the behest of one of her mom's friends, who also battled cancer. Castellano then started taping herself giving makeup tutorials and posted the videos on YouTube. One clip reached more than 8 million views, and numerous videos earned more than 500,000.
One of her dreams was to meet DeGeneres and do her makeup. In September 2012, the Emmy-winning comedienne granted the teary-eyed teen her wish and then some.
"I'm a CoverGirl," DeGeneres said on her show. "And CoverGirl heard your story and they want to make you an honorary CoverGirl. And they also want to give you something."
A stagehand appeared carrying a huge portrait of Castellano posing for the makeup brand, in addition to a $20,000 check. Castellano's image went viral online soon after.
When DeGeneres asked Castellano how she stayed positive in the face of cancer, the young girl gave a bubbly reply.
"When people ask me that, I’m [like], what do you want me to do, be depressed?" she said. "A little fishy told me, 'Just keep swimming, just keep swimming,'" referring to the catch phrase of DeGeneres' forgetful but inspiring fish Dory from the Disney-Pixar film "Finding Nemo."
Last year, when she was additionally diagnosed with pre-leukemia, Castellano posted a video predicting that she would die within the year.
"This is not fair to me anymore. I'm only 13. I shouldn't really have to be doing this. No one should have to do this, not even adults. And it's really not fair for kids to have cancer and it really freakin' sucks. It sucks so badly."
Castellano poured out her heart to fans explaining why she decided not to pursue further treatment and asking them to understand where she was coming from.
"Having cancer has been a gift, yet a horrible, horrible terrifying thing," she added. "But I've gotten so many benefits from it ... having a YouTube channel and having to inspire people and having people look up to me and explaining to you guys how I adore and love makeup -- using it as my wig -- and having so much self-confidence and going out to the grocery store without a wig. It's amazing but the journey of having cancer was amazing but every journey has an end."
Her videos are live on the video-sharing site.
DeGeneres publicly mourned Castellano on Tuesday.
"This year I met a very special girl, and today we lost her. Sending my heart to Talia's family. I'm so sad," DeGeneres tweeted.
"Thinking of my friend," she added, posting a Castellano's CoverGirl portrait on Instagram.
CoverGirl Sofia Vergara also shared her condolences.
"My heart and thoughts are with Talia, the most beautiful & inspiring @Covergirl ever and with her loving family and friends #RIPTalia," she wrote on WhoSay.
"Talia Castellano was the meaning of a true COVERGIRL," a statement said on the official CoverGirl Twitter account. "Please join me in sending love and honoring her memory."