BTW, if what you say about Munchausen by proxy is true, and I have no reason to doubt you, it is a possibility except that the Tufts doctor is a seasoned MD and is experienced with mitochondrial disorder. So you are going to have to come up with a reason for his mis-diagnosis.
It is a feature of people with Munchausen syndrome (with or without the "by proxy" part) that they will shop around until they find a doctor who will make a diagnosis. I seem to recall reading that this girl was never formally tested for mitochondrial disease, but was diagnosed based on the fact that her sister was already diagnosed. (Which raises the question of whether the sister really has the disease or is a victim of Munchausen by proxy.) I do not blame the doctor if it is the case that this girl was healthy and he made this diagnosis--people with Munchausen can be quite convincing, and the child in these cases learns how to act sick at cues from the parent.
Please keep in mind that I am not saying that I definitely think Munchausen by proxy is going on here. I am saying that there is not enough evidence to rule it out.