Continuity mistake: Anne Bancroft empties her glass of whiskey, but without filling it up from the bottle there is whiskey in her glass, and then more.
Continuity mistake: When Andy goes to see Tracy's mother, she has her hand around the whiskey glass, but when he stands up, her hand is resting on the table, and when he turns back, the glass is in her hand again.
Answer: She was posing as the mother of the little boy who lived adjacent to Andy and Tracy.
Alan Keddie