Meredith is the antithesis of a Stone. She is uptight, corporate, conservative, and allergic to spontaneity. She arrives in a starched white blouse and sensible heels, carrying a gift of "organic" gourmet sea salt (a famously terrible gift for a family that lost their sense of taste for irony). From the moment she walks in, the friction is palpable.
However, the brilliance of the film lies in how it subverts this setup. In a lesser film, the Stones would be the quirky heroes and Meredith the villainous shrew. But The Family Stone is more interested in human behavior than caricatures. As the weekend progresses, the audience begins to see that the Stones’ "warmth" can sometimes look like cruelty, and Meredith’s "coldness" is a shield built of anxiety and insecurity. The film forces us to ask: Is Meredith wrong for who she is, or are the Stones wrong for refusing to let her in?