First of all, sorry to hear about your family, I hope they recover soon. Symptoms usually last around 14 days, but the cough can stay for weeks after, so fingers crossed they're on their way.
The worst thing about this virus is that alot of people assume it's being built up, that it isnt as bad as they think or they wont catch it because they dont know how viruses work, especially a respatory one with no treatment.
The only way these people will learn is by experiencing it first hand, like your sister has. She is guilty of being naive about the virus and had put them at risk for the sake of earnings, but her admittance of guilt wont change anything. I'm sure secretly she is feeling really guilty and if anything bad happens it will crush her.