Last Updated Jun 12, 2013 4:21 PM EDT
Updated 4:15 p.m. ET
A lung transplant is being performed on Sarah Murnaghan, a 10-year-old girl whose family sued to get her added to an adult lung waiting list.
Family spokesperson Tracy Simon confirmed the transplant was taking place Wednesday to CBS News.
"We are overwhelmed with emotions!!!!" Murnaghan's mother Janet wrote on her Facebook page Wednesday. "Thank you to all of you for the unending support."
Sarah is being treated at the Children's Hospital of Philadelphia.
Janet told CBS News Wednesday that the family received a call Tuesday night from the hospital telling her there was a match for Sarah.
"It was a very exciting moment, but also a little bit cautious moment because this is our fourth time being told that," she said.
They only found out 15 minutes before they took Sarah into surgery Wednesday that the procedure was guaranteed to take place. The family does not know any details about the donor, she added, but she calls the person an "amazing selfless hero." She added the lungs came from an adult or teenage donor -- someone over 12-years-old.
The procedure can take up to 8 hours, according to Janet. Doctors told her the hardest part of the surgery is removing Sarah's lungs which have been badly damaged and scarred by cystic fibrosis.
Last week, Sarah wasfollowing a ruling from a federal judge Michael Baylson that suspended rules that required patients on the adult transplant list to be ages 12 and older.
The girl had end-stage cystic fibrosis and only had weeks to live, her family said at the time. Since Saturday, Sarah has been in a coma, her mom said.
"They had stabilized her but she was in critical condition and we just weren't gonna have much more time, so this is really just an amazing blessing," Janet said.
The Murnaghans had sued to challenge current U.S. transplant guidelines that state people aged 12 and older are ranked in order of need to determine who will be the top candidate for an adult organ transplant., because everyone 12 and older in the region who had her daughter's blood type would be offered the lungs first, even those who may not be as sick.
The family started a petition on Change.org, and called on Secretary of Health and Human Services Kathleen Sebelius to intervene. of the transplant guidelines and how they affect children.
-- citing that other children at the same hospital were just as sick and many complex factors go into how transplant lists are created -- the family took the case to court.
The court's ruling triggered another lawsuit,, who also has end-stage cystic fibrosis. He too was then added to the adult transplant list.
Nationwide, about 1,700 people are on the waiting list for a lung transplant, including 31 children under age 11, according to the Organ Procurement and Transplantation Network (OPTN). Pediatric lungs are rarely among those donated.
The judge's ruling set off anwho worried about the precedent being set of a legal-driven exception that could trump evidence-based transplant guidelines. Lung transplants already have a high failure rate -- 50 percent within five years -- and since lungs are in short supply, some bioethicists argued transplants should be given to people who have the best chance of success. And since pediatric lungs are less well-studied, there may be more medical certainty of the transplants taking in adults.
"It would be very difficult that this system has to respond for individual pleas for help," Dr. Margaret Moon, a pediatrician and bioethicist at Johns Hopkins Medicine in Baltimore, said to CBSNews.com last Friday. "Every story is compelling. It's always tragic when someone doesn't get an organ -- that can't be a reason to change that approach," she said.
Dr. Art Caplan, head of the division of medical ethics at New York University Langone Medical Center in New York City, added to USA Today, "The best place to make medical decisions is not in a courtroom, it's not in Congress, it's not on television." He said, "It's with doctors and people with expertise in transplants making the decision based on how well the transplant will work and who is likely to live. Those aren't facts that judges, senators or bureaucrats have."
Following the public debate, theto hear individual cases such as Sarah's and Javier's. The network rolled that system out instead of making emergency changes to the current age limits on adult transplants.
Since 2007, only one lung transplant in the United States had occurred from a donor older than age 18 into a recipient younger than 12, according to OPTN.