Several hours later, DeGeneres posted an image of Castellano in a mock-up of a CoverGirl ad to her Instagram account, with the words "In Loving Memory" printed across the bottom. In the heartbreaking photo, Castellano shows off her trademark bright smile.
The Orlando teen first sat down with DeGeneres, 55, on her show in September 2012 after fans of the YouTube star's makeup tutorials started a grassroots movement to make Castellano's dream of meeting the talk show host come true.
"You really are quite something. There's a depth to your soul that is not a 13-year-old soul," DeGeneres observed at one point during their interview. "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."
Castellano was diagnosed with neuroblastoma six years prior to her death, and had more recently been diagnosed with myelodysplastic syndromes (MDS), a condition formerly known as preleukemia. During her interview with DeGeneres, however, the teen expressed nothing but positivity about her situation.
"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," read a heartfelt message on her Facebook page. "We will miss you more than you will ever know, baby girl."