Given the following context:  Celia Crowson and her family go on holiday to the south coast of England in the summer of 1939. Soon afterwards the Second World War breaks out and Celia's father joins what was to become the Home Guard and her more confident sister Phyllis joins the Auxiliary Territorial Service.  Fearing her father's disapproval if she moves away from home, Celia hesitates about joining up but eventually her call-up papers arrive. Hoping to join the WAAF or one of the other services, Celia instead gets posted to a factory making aircraft components, where she meets her co-workers, including her Welsh room-mate Gwen Price and the vain upper middle class Jennifer Knowles. Knowles dislikes the work they have to do at the factory, causing friction with their supervisor Charlie Forbes which eventually blossoms into a verbally combative romance. A nearby RAF bomber station sends some of its men to a staff dance at the factory, during which Celia meets and falls in love with an equally shy young Scottish flight sergeant Fred Blake. Their relationship encounters a crisis when Fred refuses to tell Celia when he is sent out on his first mission, but soon afterwards they meet and make up, with Fred asking Celia to marry him. After the wedding they spend their honeymoon at the same south coast resort as the Crowsons went to in 1939, finding it much changed with minefields and barbed wire defending against the expected German invasion.  answer the following question:  Who is the sister of the woman that the flight sergeant asks to marry him?
Answer:
Phyllis