By “a tiny life,” Mrs. Winterbottom likely means a life that’s limited, unfulfilling, and unimpressive. By asking this question, the reader can infer that
she thinks she leads a tiny life, and that she’s probably hoping someone will tell her that she doesn’t. When both Prudence and Phoebe brush their mother off, they essentially show her that she does lead a tiny life—her world is limited to being a wife and mother, and she’s unappreciated and taken for granted within this role.