The decorator was the woman attempting to help Sun escape her husband Jin, but later attempted to talk Sun out of leaving. She eventually gave in to Sun's intentions, and decided to help her.
She promised to look after Sun's dog once she had gone, and gave Sun a fake passport and documentation. She had also arranged her escape. She forced Sun to repeat the time of the escape over and over "11:15".
Originally in Korean:
DECORATOR: Your husband told me that money is no object to redecorate this place. You're a very lucky wife.
JIN: Move the dog.
SUN: Let's look at the apartment from the bedroom, shall we?
DECORATOR: Are you sure about this?
DECORATOR: You've taken your lessons?
DECORATOR: Do you realize that your husband and your father will do everything they can to find you? Are you sure you and your husband can't reconcile?
SUN: When I'm gone will you care for my dog?
DECORATOR (Hands Sun a Passport): During your trip, at the airport, at 11:15. . . You make an excuse and walk out of the airport. Bring nothing! A car will be waiting. For the first week your family will assume you've been kidnapped. You will stay out of sight until they come to think you are dead. After that you will be free to move wherever you want. Now, tell me when.
SUN: The airport, 11:15.
SUN: 11:15. 11:15. 11:15.