Fifi offers a pleasant smile, ever prepared to remain in the background, to enhance the experience of the men around her until she's needed (and all the better to listen to everything they say). When Vincent introduces herself, she rises to give a little curtsy, extending her hand to him in the delicate Orlesian fashion.
"Josephine Mariette," she replies, "it is a pleasure, messere." She doesn't look at Bastien, but can feel him, and what's behind his expression, as brightly as one perceives warm sunlight.