Coughing in public

If a 10 year old hadn't been taught by her parents to obviously always cover her mouth when coughing especially around other people eating, when will she learn?

Parents were near her and didn't tell her to cover her germs & to make it worse she sounded chesty and pretty sick.

I know it is a bit of a rant but respect for parents, siblings, friends, family and strangers should be taught and corrected until learned from an early age. It is fairly disgusting to cough near someone else's dinner