She has a rare disease that's almost always fatal, severe aplastic anemia, which prevents her body from producing blood cells.
Doctors told Kailee's parents there was only an infinitesimal chance of saving Kailee's life, and.
But, reports The Early Show co-anchor Hannah Storm, finding a match seemed almost impossible because Kailee was adopted from China and her blood relatives couldn't be found.
Still, her parents embarked on a long, far-flung quest for the perfect donor.
"The odds of matching Kailee were about 10 million in one," Owen Wells told Storm.
But the odds would not deter Owen and Linda Wells.
"No one believed it was ever gonna happen," Linda says.
Linda and Owen began with a Web site, spreading the word about Kailee. Soon, they were trying to register marrow donors everywhere.
"They told us in the very beginning that we shouldn't even bother to do drives," Owen says, "because it would take our resources, our energy, our time away from our child."
"But," Storm asks, "when someone says something like that to you, what was your reaction as a parent?"
"Well," Owen says, "my reaction was, 'B.S.' We have to try. You know, we may not succeed, but we have to try."
Owen set up marrow drives around the country helping to register more than 5,000 donors and finding at least a dozen matches for other patients. But none for Kailee.
"What we're encouraging is for adults to consider doing it one time in your life," Linda says. "And personally, I think it would be the greatest honor for someone to call me and say that I'm a match."
Linda made several trips to China, desperately seeking a match for Kailee. After three-and-a-half years, their work paid off. Wang Lin, a 28-year-old doctor, turned out to be a near perfect match.
In Beijing, he donated blood stem cells that, when placed in Kailee, promised to help her body kick-start the production of its own blood cells.
"For 45 months," Owen says, "we'd been trying and trying and trying to find this miracle man, this wonderful person who matched Kailee. And to actually have it happen, we're still kind of in disbelief."
A courier collected the donation in China and hand-carried it back to the Children's Hospital of Wisconsin, in Milwaukee.
Dr. David Margolis managed to keep Kailee alive with various treatments, all the while hoping for a transplant.
Earlier this week, Margolis said: "Today is definitely the day we've been looking for for three years. Absolutely. Because nothing afterwards can happen if we don't have the cells. And this time, we have the cells from as well matched a donor as anybody could have."
On the day of the transplant, Kailee underwent radiation treatment. Her immune system had to be destroyed so it won't attack the foreign blood cells her body was about to receive.
"She was a little frightened as they were getting ready for the procedure," Owen says, "but she was a brave little girl, and she stood up to the test and she did it."
The donation, frozen in liquid nitrogen, was carefully thawed and prepared.
The procedure itself, a simple blood infusion, was a success.
But, Storm points out, there are still many obstacles to overcome.
"Based on the best data that I can put together," Margolis says, "I think that Kailee has a 50 to 70 percent chance of meaningful quality of life, long-term survival."
The first question, Storm says, is: Will Kailee's body accept the donation? If so, will the cells begin to grow? It will be weeks, likely even months before the answers are known but, for now, there is hope.
"If I look at the future, it's too scary," Linda concedes. "If Owen looks at the future, he sees that she'll get better. … So, we both learned to deal with that by living for today; that today, she is going to have a good day; that today, we are going to enjoy our time with her."
In honor of the Wells family, The Early Show organized a marrow donor registration drive in the show's plaza at Manhattan's General Motors building.
The National Marrow Donor Program's Patrick Thompson told Storm registering to become a marrow donor is easy.
"It's filling out a consent form and giving us a small sample of your blood," Thompson says. "The more people who join the registry, the greater the chance is of people who haven't found a match to find a match. The blood is put into our system and matched up with people who need a transplant."