The New England Journal of Medicine just published a study that tested how long the virus can remain stable on different kinds of surfaces within a controlled laboratory setting. They found that it was still detectable on copper for up to four hours, on cardboard for up to 24 hours, and on plastic and steel for up to 72 hours.

It sounds like your friend needs to continuously rub her hands with copper for at least a few hours in order to deactivate this particular coronavirus. Alternatively, she could just wash them with soap and water ;-)

On a more serious note, she may have started doing this based on research conducted 5 years ago on other types of coronavirus, which suggested that copper surfaces in communal areas (as opposed to stainless steel) would help slow the spread of viral infection. https://www.sciencedaily.com/releases/2015/11/151110102147.htm

This research was not done on novel coronavirus, however, and the research we do have suggests that, while it does deactivate more quickly on copper than on other surfaces, there’s still no substitute for hand washing and sanitizing.