So, i agree, and i disagree.
One of the important points that i think people are missing, is that family and close friends are going to be the ones who can detect the onset and severity of problems. They should inform their doctors about this (and to some extent this woman did with the "spidey sense" thing).
Doctors are not in a good position to tell how far out of the norm a child is in terms of their daily life, unless you and your child see that doctor on a regular basis. It may very well be that one's social network (especially if your social network is lucky enough to include a pediatrician and a cardiologist) who are familiar with your child may be better suited to picking between two overlapping diagnoses.
Given the prior probabilities, and no specific information or identifying features doctors are going to err on the side of the most likely symptom causing disease. In this case, if it looks like strep, and the doc has no further info, it probably is strep.
tl;dr: You know your family better than your doctor does. Your doctor knows medicine better than you do. :P
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All that said, I think it's important to note a few other things. Generalists (general practitioners, pediatricians, ER docs and the like) and Specialists (cardiologists, for instance) have different biases in diagnosing. If the author's friend had been, i dunno, a dermatologist rather than a cardiologist, she may have offered a different, and likely incorrect suggestion for diagnosis. Hard to say.
Doctors, like any other science can have biases (i do not mean that in the pejorative fashion), especially when it comes to identifying rare conditions/circumstances.
Lastly, this is really social networked medicine at it's best. Mom has a sick kid, she's snapped some photos to text to her doctor, why not post them for her friends (who have medical expertise) to look at too? As in the ideal case, the concerned friends with medical experience followed up with mom to keep abreast of changes in the kid's condition, and upon noticing that symptoms were not improving, and were perhaps getting worse, suggested that (out of an overabundance of caution) that mom needed to take kid to hospital.
In that regard, none of the behavior here is outrageous or egregious (except that her husband is a bit of a knob).