Sheila Carter, by wikipedia® definition is playing the role of villain –
Villains in fiction commonly function in the dual role of adversary and foil to a story’s heroes. In their role as an adversary, the villain serves as an obstacle the hero must struggle to overcome. In their role as a foil, they exemplify characteristics that are diametrically opposed to those of the hero, creating a contrast distinguishing heroic traits from villainous ones.
Other have pointed out that many acts of villains have a hint of wish-fulfillment, which makes some readers or viewers identify with them as characters more strongly than with the heroes. Because of this, a convincing villain must be given a characterization that provides a motive for doing wrong, as well as being a worthy adversary to the hero. As put by film critic Roger Ebert: “Each film is only as good as its villain. Since the heroes and the gimmicks tend to repeat from film to film, only a great villain can transform a good try into a triumph.”