Who is Cyndi from Taft and what is their importance?

Cyndi is one of John Nickel's longest-serving waitresses at Muddy's. She is ill-tempered and hard-drinking and regularly antagonizes John, who nonetheless considers grooming her for management. He changes his mind, however, once she twice arrives drunk to work and begins a relationship with Carl Taft, whom she knows is selling drugs. When she is moved, Cyndi does an elegiac hula dance like the one she learned working in Hawaii.