Answer:
Because she died in a car accident, two weeks before home, her death was very painful for Annemarie's parents and they believe it may have been linked to the resistance to the German invasion.
Step-by-step explanation:
Anniemarie's older sister Lise was 18 when she died and was entering a new phase in her life, as she was to be married in two weeks. He was excited, full of plans and happy. Her death was a very unfortunate moment for the family who loved her very much and talking about it causes more pain and remorse. They also have doubts as to whether her death was really an accident, or whether it had any connection with the resistance to the German invasion.