That is not necessarily true. I have had pneumonia and was sent home on inhalers and oral antibiotics. Granted I was younger than Hillary, but I felt like crap for at least 2 weeks.
Did you faint or lose consciousness?
If this was a bout of pneumonia and she had collapsed like that, she would have been medi-vac'd to the hospital.
No, the Secret Service is fully apprised of her condition (whatever it is) and they were not surprised by this event at all. They handled this like her falling over is a regular and expected event.
This appears to be something they are quite used to seeing.