The charismatic, honorary CoverGirl Talia Castellano passed away Tuesday at age 13.
The teen stole Ellen DeGeneres' heart as a guest on her show to speak about her brave battle with neuroblastoma for more than six years.
DeGeneres addressed her sadness on Twitter saying, "This year I met a very special girl, and today we lost her. Sending my heart to Talia's family."
DeGeneres told CoverGirl Castellano's "inspiring" story after her makeup tutorials on YouTube got more than 15 million views. The brand made her an "honorary CoverGirl."
CoverGirl tweeted Tuesday, "Talia Castellano was the meaning of a true COVERGIRL."