NEWTOWN SQUARE, Pa. (CNN) -- Once again, the Murnaghan family is complete.
After six months in the hospital fighting for her life -- during which her parents fought to change national policy on organ donation to save their now 11-year-old daughter's life -- Sarah Murnaghan returned home to Newtown Square, Pennsylvania, on Tuesday.
"She just wanted to be with her brothers and sister," her mother, Janet, told reporters. "I mean, she really just wants to be with her family. It's been hard."
Then again, life has never been easy for young Sarah.
She suffers from cystic fibrosis, a disease of the secretory glands that's passed through genes -- even if the parents of the person afflicted don't have it. According to the National Institutes of Health, the disease often affects sufferers' lungs, pancreas, intestines, liver, sinuses and sex organs.
In mild cases, a person with cystic fibrosis may not be diagnosed until they are teens or, perhaps, adults. But for others, it can have a debilitating impact.
That was the situation with Sarah, who has been in and out of hospitals her entire life. Speaking Tuesday, Janet Murnaghan credited the diagnosis with making her daughter especially tough.
"It's a disease that's really demanding -- ... it takes everything from the minute you're diagnosed until you're at the point where Sarah is at," the mother said. 'She's spent her whole life fighting. It's just a different mentality than your average kid."
Even then, the past year has been particularly difficult. Sarah's lungs had deteriorated rapidly -- much faster than anyone in her family expected -- and in May doctors told the family that Sarah had less than five weeks to live.
Despite her dire condition, though, Sarah couldn't get a lung transplant. She was the first candidate on the priority list for children in her region.
But children's organs rarely become available. In 2012, there were just 10 transplants in Sarah's age group, according to the United Network for Organ Sharing. Comparatively, there were more than 1,700 adult transplants in the same year.
Her family felt transplanting an adult lung was their best hope. But it wasn't possible: Sarah fell just shy of the requirement that anyone who gets adult lungs must be at least 12 years old.
Perhaps taking a cue from their daughter, the Murnaghans fought vigorously to change that stipulation -- and like her, they succeeded. On June 5, a federal judge issued a restraining order to prevent the U.S. Department of Health and Human Services from having the agency that oversees transplants apply the policy.
HHS Secretary Kathleen Sebelius then directed the Organ Procurement and Transplantation Network to waive the rule.
Even after that move, the Murnaghan family is vowing to keep working so youngsters get every medically sound opportunity available to get transplants.
"Kids on the system have died at three times the rate," Janet Murnaghan said. "So we're not letting go of it."
June happened to be a particularly tough month for the Murnaghan family in many ways: Not only were they initially waiting for a policy change, but Sarah -- then 10 -- was clinging to life.
Their dreams appeared to come true that month as well, when she received transplanted lungs -- from an adult . But it didn't take, the family revealed later. For several days, a machine kept Sarah alive.
She got another chance in the form of a second lung transplant, which again came from an adult. Speaking more than two months after that happened, Janet Murnaghan said "the lungs are doing fabulous."
"She's weaned off the oxygen," the mother said. "But she has the tracheotomy, (which) is helping her breath... They just can't do it by themselves yet."
With her discharge and ambulance ride home from Children's Hospital of Philadelphia, Sarah is back where she belongs. But it's not like things are all of a sudden easy for her. She still has trouble walking, relying on a walker to move. She will head off to rehab several times a weak.
But Sarah will also start school -- from home, initially -- the week of September 9. If all goes well, things will keep on progressing, says her father, Fran Murnaghan, who adds hat the goal is "getting more back to regular life.
"Each day, she gets stronger," he said. "We'll be doing more and more normal things."