(CNN) -- When she was healthy, Olivia Wise used to sit in front of her locker at school and sing for her friends.
She loved learning new things, and she wanted to be a pediatrician.
Olivia is just 16, and she is dying of an inoperable brain tumor.
In September, knowing that there was no more treatment available, the Toronto teen went to a recording studio to immortalize her voice -- one that has brought to joy to her family and friends in her short life.
She sang Katy Perry's hit "Roar."
In the video made of her recording, she sits meekly in a wheelchair, unable to stand or catch her breath.
And then she gets to the first chorus.
" 'Cause I am a champion, and you're gonna hear me roar."
Her eyes squint, and a smile stretches across her face.
Her joy is infectious. People in the studio begin to dance.
As the song goes, Olivia sings, "I got the eye of a tiger, a fighter, dancing through the fire."
A few more chords, and the corners of her mouth rise again.
"Olivia is a fighter and has gone through the fire," her cousin wrote in the post under the video posting on YouTube. "In fact, she was going through the fire while she recorded this song, but you wouldn't know it, because she was dancing right through it."
That recording was made on September 6. In the weeks that have followed, Wise's condition has deteriorated, but the response to her video has gone viral. The Liv Wise Fund, started in her name in support of brain tumor research, has raised more than $27,000, and the video got enough attention to prompt a response from Perry about how moved she was by Olivia.
"You sounded great," Perry said in a video she sent to the family, which was also posted to YouTube. "I love you. A lot of people love you. ... Keep roaring."
Wise is at home now, and her family is making her as comfortable as possible. She is only conscious for moments at a time, her family said.
"Her health is really bad, she's at the end," her cousin Jeff Kassel said. "She is still conscious at times and taking it all in."
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Wise was vacationing in Florida in January 2012 when she had a seizure. She was diagnosed with a very aggressive form of brain cancer.
Immediately, she knew the prognosis was bad, but her mother says she has barely complained.
"Every day, she wished for a cure, and rarely succumbed to negative thoughts," her mom said.
She insisted on keeping up with her studies until just a few weeks ago.
"To tell the truth, her diagnosis didn't change her personality," her mom said. "It only enhanced it. She took the news in a mature, reasonable, responsible way. ... Even in the most difficult moments, she managed to bring laughter and friendship to all that were caring for her."
She woke up each day with a goal to find something bright, to be happy, her mom said. And she wasn't afraid of being vulnerable.
So when a family friend with a recording studio offered her the opportunity, she went for it.
"It was spontaneous," Kassel said. "And we didn't know with her health if she would be able to do it, but she did. For a 16-year-old, this is becoming her legacy, and it's such a beautiful thing."