Who is The Store Clerk from Long Time Coming and what is their importance?

The store clerk was encouraging to Marnie, telling her that a certain dress looks incredible on her. When Marnie checks the price tag, however, she admits that she can't afford it and tells the clerk of her decision. As a result, the clerk pulled a pen out of her pocket and marked the dress down to half price, telling Marnie that the dress is perfect, and that she is still making a profit at that price.