A day later, Lee's mother, Esther, posted an update on a Facebook page documenting her leukemia treatment, called Team Brighter Days, that Lee's PET scan came back "clean."
They're now able to move forward with the bone marrow transplant, which has been scheduled "in the next few weeks."
Esther Lee said her daughter has been longing to create vlogs and "this was just another moment of wanting to ask people to pray for her in her great time of need."
Lee has been waging her battle with cancer since 2014. That's the year she was diagnosed with a "super rare" form of leukemia, Esther Lee told ABC News.
Her mother added that after finding the right chemotherapy to work, her daughter went into remission for 10 months before she relapsed with a form of cancer "only in her skin." By March 2016, the cancer had spread to different parts of her body.
Lee's PET scan on Thursday, in which she solicited prayers for, was able to tell doctors if she's a good candidate for a second bone marrow transplant.
Although Lee's testing resulted in good news, her mother told ABC News that her "chance of survival" is still between 5 and 10 percent.
"She’s always been super positive about it, but it’s been almost three years fighting and she's not really been able to live a normal life," Esther Lee admitted. "It’s wearing down on her."
The mother of three said she recently had to have a "very serious discussion about possibly not being able to do more." She added that Ava was most upset when she realized she'd be apart from her parents.
"That was her main sadness. She was really broken up about that. [That's when] she asked for prayer," Esther Lee added.
Esther Lee, 36, said her daughter's faith comes "second nature" since her husband is the pastor of a non-denominational church called North Shore Chinese Christian Church in Deerfield, Ill.
"I truly believe that’s what has allowed us to not completely unravel during this really, really difficult time," she said. "That’s the only thing that brings her comfort -- when we talk about there’s hope for her future apart from the life that we have here."
It also helps, Esther Lee said, that Lee's video has received thousands of comments.
"I envision thousands of people surrounding us, even as we sit in this room, and collectively praying for her," she said. "And what a sight that is...because we know that we’re not alone."
Esther Lee hopes that by sharing Lee's story she can bring awareness to what pediatric cancer patients go through -- describing it as "truly hell."
"Someone needs to know what’s happening. Even my words are not enough," she continued. "We need to do more. There needs to be more humane ways of treating children with cancer."
Describing the aftermath of one radiation treatment, Esther Lee recalled, "I couldn't even hold her for 10 minutes because of the radiation emitting from her. All of this is happening to my child. And you don’t have a choice as a parent."
Esther Lee hopes that with more pediatric cancer funding, there will be more research done to create new ways to treat cancer in children.
"It’s so hard to imagine what these children go though. They're the bravest children I’ve ever, ever met," she said.