The few clues that we have about Marie's personality come from Meursault, but he is not given to analyzing himself or other people and so we know little other than that she seems, basically, an uncomplicated middle-class young woman. She wants marriage, children, enjoys casual sex, swimming, movies, and outings to the beach. She is frightened and terrified when Meursault is arrested; her life, one would guess, has never been confronted with such drama. Like Meursault, she has had rather unimportant jobs: he is a clerk, she was a typist. She is attracted to Meursault because he enjoys many things that she does and also because he is a little "different." When Meursault agrees to marry her, Marie is happy. Meursault will probably be an adequate husband; he will probably have a steady job, an income that she needn't worry about, and she doesn't ask much more from a man. Like Meursault, she does not demand much from life or from other people.
Marie is on the fringe of this novel, even though Meursault has agreed to marry her. But one should remember that she had great hope for her new life in Paris with Meursault. She is much more of a romantic than he is. She has her daydreams and is happier than we have ever seen her. When Meursault is arrested and sentenced to death, her dreams also die. Later, she is obscured by Meursault's introspection, and she drifts away, from the plot, from Meursault, to everyday life and everyday routine.