The first thing that sticks out is that people are calling for an "exception to the rule". I put that in quotes since it's not really what we're talking about. This isn't an exception to a rule, but a blatant disregard for a system put into place to ensure fairness. The whole point of an external decision-making system is to remove the onus from the decision maker on an individual basis. The decision was previously made that candidates awaiting lung transplants would be ranked according to a certain set of criteria. To make an exception is to set a precedent to that rule. One would then have to make a set of rules that govern when someone can circumvent the process. Agreed upon rules or processes are a covenant signed by our society that ensure that equality exists no matter the situation. If you allow for exceptions, why have a rule in the first place? We should then just make the rule that we'll decide on a case-by-case basis.
Alright, so an exception doesn't seem ethically feasible. Another suggestion was that the rule needs to be changed due to its "unfairness". It does at first blush seem unfair that a little girl should die waiting for available lungs. But we have to be careful how we use this word. I think that sentiment expresses a meaning emoted in the phrase, "The world is unfair." The world obviously cannot be fair or unfair, since it is not a rational agent. The world just is. In that case, I think we need to substitute the word and say, "Things that happen in the world make us sad." It is then sad that a little girl might die because she has a horrible disease that can only be treated with an organ transplant that is hard to come by. It is not, however, unfair or unjust just because it makes us feel sad. Fairness and justice are concepts reflecting a very cold and calculated outcome. There's a reason that the statue representing justice has its eyes covered. Justice should be blind to the plight of the individual, if that means special privileges based on something other than the criteria put forth to judge that situation.
The toughest thing in ethics is to be the person to say, "I'm sorry, but the answer is no." I'm sure everyone feels for this girl and feels for the parents and feels for the physicians who want to help. The biggest problem with rules is that people like them until they're the ones who are negatively effected by the rules. I'm perfectly OK that the Navy has a cut-off for height for submariners and fighter pilots. I am, however, not in the Navy. Is it unfair that since I am over 6 feet tall that I can never serve in one of those capacities? I don't really care, as I don't desire to fly in an F-22 or be 20,000 leagues under the sea. Most would even think it was silly for anyone to even fight that regulation, since you cannot physically fit in either of those roles if you are over 5'10" (full disclosure: I have no idea any of that is true, but it sounds reasonable enough to use as my example). This goes all the way back to the foundations of philosophy. I won't go into the Trial and Death of Socrates, but he essentially supports the same thing. Even though it sucked that he was sentenced to death by a kangaroo court, that was the system he lived under and enjoyed the society it supported, so if that system decided he should die then he had to abide by the rules.
Finally, the list is built on medical feasibility. They could use adult lungs on this little girl, but the chance of her body accepting them is much less than if they were given to an adult. That's the reason the rule exists. If I were to be the next person in line to get a set of lungs and someone got to butt in front of me because of public outcry, let's just say I'd be a little upset. I'd be a lot upset if I found out they gave it to a candidate that had a much less better chance of surviving than I did. In sum, rules are rules, ethics is hard, I feel bad for everyone in the situation, but I don't agree with them.