My coworker has had scabies for a month and refuses to get treated knowing she contracted them. She insists they will die on their own. Totally false?

Totally False! Scabies are easily transmitted, can affect "very" uncomfortable areas of the body and need to be treated in order to be eradicated! your coworker is unfortunately deluded!
Itchy. Have the coworker get treated so that the risk of spread to other employees is minimized.