Hi there -
While the yellow powder in an ABC fire extinguisher (monoammonium phosphate) is generally considered safe and routinely gets inhaled by the operator and bystanders when used, the inhalation is not recommended (for obvious reasons). Usually, at most, what may be expected is some slight airway irritation, but rarely anything more than that. The only possible exception is the one pregnant girl, who may want to mention the incident to her obstetrician, just to be on the safe side. Everyone else should be fine.
Hope this helps answer your concern. Best of luck to you.
John Kenyon, EMT, CCT
Non-invasive cardiology tech, Emergency and Critical Care technician, Critical Incident Stress Mgmt. specialist