Reiko's actions reveal her loyalty to a strict moral code.  She apologizes for her 'unfilial conduct in thus preceding her parents to the grave;' her personality seems determined to please, and even in death she apologizes to her parents for her behavior. 

Reiko is also very young, only twenty-three years old.  The reader could infer that she might be still very naive about love and marriage, since she had only been married for less than half a year.  When Shinji lectures her on wifely responsibilities on the eve of their marriage, Reiko responds in kind, showing him the dagger from her mother, reassuring him that she knows her duty.  This detail reinforces Reiko's character as a woman desperately seeking her role in the home and eager to please her new husband.  The lieutenant is "the sun about which her whole world revolved."