Differential diagnosis is still a practiced thing though, yes?
From Medscape:
"Older children [leading on from a section about toddlers and preschoolers] and adolescents may also present with fever, cough (productive or nonproductive), congestion, chest pain, dehydration, and lethargy. In addition to the symptoms reported in younger children, adolescents may have other constitutional symptoms, such as headache, pleuritic chest pain, and vague abdominal pain. Vomiting, diarrhea, pharyngitis, and otalgia/otitis are other common symptoms.
So, whilst she got the chest x-ray ordered, surely, in such an ill child, reviewing it so late after it was done was not a good idea, because pneumonia should have been one of her prime differentials? Especially as the child was breathless, required oxygen and had 4 of the common markers for pneumonia?
Gastroenteritis was a reasonable diagnosis to be running with until the moment there was evidence to show otherwise, but the delays in treatment cost him his life, and "drinking from a breaker" is not a reliable clinical assessment of health.
However, I do think she was failed. In my hospital, if a chest x-ray is very bad, the radiographers will telephone the ward and report that the result is ready, it needs to be reviewed, and take the name of the person they have spoken to. Likewise, if a blood result is badly deranged, our labs will telephone the ward, report the result, repeat the result, ask you to confirm the result you have heard, and ask for your name. They won't just shove it on the screen and hope you see it.