Who is The Mother (Marie Legrand) from The Lover and what is their importance?

Marie Legrand, the narrator's mother, is a dominant character in the novel noted more for her absence and emotional distance than for an active role in parenting. She runs a French-language school when the narrator meets the lover. Marie has been married at least twice—the first time to a Mr. Dark, the second time to the unnamed father of the narrator. She has three children.