(NBC NEWS) -- The little girl who made national headlines after winning a fight to get on the adult lung transplant list has spent her first day with a new set of lungs.

Sarah Murnaghan's surgery was a success, but her recovery is likely to be difficult.

Sarah cheered when she heard the news she would get a new set of lungs.

An adult donor was identified on Wednesday, and after a successful transplant, Sarah's aunt says doctors need her to take her first breath on her own soon.

"It happens pretty fast, because they've got to get those lungs working as fast as they can," said Sharon Ruddock.

Prior to the surgery Sarah had just days to live because of badly damaged lungs from cystic fibrosis.

Now her family says Sarah's fighting spirit will help get her through the next phase of recovery.

"It's painful, it's difficult, but Sarah has always said she was not going for easy," Ruddock said. "She was just going for possible."

The surgery was possible because of a court order getting her onto a transplant list for adult donors.

A national group of doctors and medical ethicists manage the limited supply of donated organs. The group voted to allow special consideration for very sick children to get on adult lists after the Murnaghans and another family filed suit.

"We now have a new avenue, and it's a scary one allowing judges to make decisions about who lives and who dies rather than a system that strives to be as fair and transparent as possible," says Stanford University bioethicist David Magnus.

The rules are in place in part because adult lung transplants can be risky in small children, but young donors are rare.

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