Yeah the crew is not involved but if the passenger is on the plane and there is a health concern (such as in this case where the SW flight attendant did not like what she saw) we have the gate agent call Medlink to clear them. Ive had it go both ways, sometimes they say the pax is good to go, sometimes they are not. They can obviously call while in the gate area as well, but like most gate agents, they tend to let it all get boarded and let the sick person, drunk, etc play peek a boo with the Flight Attendant to be found fit to fly.