Histio,
This is absurd, and a potential medicolegal nightmare of a physician. You know, with breast cancer, the most common legal consequences occur when breast cancer is missed. And this usually happens in the context of a practitioner who is doing a breast exam specifically looking for a lump, or looking at a mammogram to specifically try to find a mass palpated on exam. Now imagine how you would defend yourself in court if the radiologist already told you there was a lump there, and you still failed to decide to treat?
Likewise, in your story, the diagnosis was essentially given to her. If the machine shows 100x normal ketones in the urine... guess what? The patient is in ketoacidosis!!!!!!!!!!!!!!!!!!!!!!!!!!!! The diagnosis was already made for her, she still failed to see it, went out of her way to make up another 2 diagnoses, with hopes to use her clinic machines, and then humiliating her medical student for actually being right and possibly saving the patient or improving his morbidity.
You should report this attending to your medical school.... if not because she will likely lose her license to something stupid in the near future, then because there is clearly very little that a third year student will be learning from her expertise... or lack thereof