Although her kind of cancer normally has an 85 per cent cure rate, Emily's leukemia kept coming back, despite rounds of chemotherapy.
And just when her family thought they may lose her, she was approved to take part in a clinical trial being done at Children's Hospital in Philadelphia and the Hospital of the University of Pennsylvania.
Emily became the first CHILD to receive a new kind of gene therapy that could change cancer treatment.
The therapy re-engineers a patient's own T-cells - vital cells in the immune system - to attack cancer cells.
Doctors at CHOP say that 3 weeks after Emily got the infusion, the leukemia was gone.
But she still faced a big hurdle. The treatment caused side effects, including a sky-high fever, pain and dangerously low blood pressure.
The rampaging T-cells unleashed other disease-fighting compounds in her body which attacked her red blood cells.
Doctors turned into detectives, using their computers to find a drug that would stop the attack.
They found their match in tocilizumab (Actemra), a new rheumatoid arthitis drug.
With that toxic episode behind her, Emiliy is now enjoying a normal childhood life.
Mother Kari says, "She''s happy and healthy, and this fall, returned to school."
Dr. Stephan Grupp, of CHOP says, "This is a fundamentally different way to treat cancer. And I believe this is extremely exciting, at least for patients with these types of cancer with B-cells - the leukemia and lymphoma."
So far, 10 leukemia patients have received the new treatment at the Children's hospital and the Hospital of the University of Pennsylvania.
Four patients have seen their leukemia completely wiped out, several for as long as 28 months. The treatment, called CART 19, has worked in all but two cases. But doctors now say they know why it didn't work in those cases.
And they believe they have a way to work around that.
The new technique has excited cancer researchers around the world since it was first announced in August 2011.
Earlier this year, Novartis and Penn entered a commercial partnership to bring it to the market.
Dr. Grupp says this a a new area for pharmaceutical companies, too, because it involves cells, not the medications they are usedd to handling.