Context:
Lady Macbeth is usually seen as the driving force behind Macbeth's ambition but Sian Thomas was concerned not to play a cliché. She felt that for the character to seem wicked would be predictable and allow the audience to dismiss her as evil personified. So instead her focus was to try to balance the two sides of the character and make her identifiable and real.
Did you know? An actor has to wear a character like an extra skin, fitting her own body and personality into the shape of the character as tightly as possible.