Pippi Vallier, whose name is given as Pipi Barlier in the anime and its source materials, with Pepi Barlier also used as an alternate spelling, is a minor supporting character in I'm in Love with the Villainess. She is a student at the Royal Academy in the Bauer Kingdom and the heiress of the Barlier family, a household with deep connections and considerable influence in the kingdom's business world. She grew up as a childhood friend of the noble Claire François, and that long history is central to her place in the story.

In appearance, Pipi has short pink hair, light blue eyes, and pale, milky skin, and she is almost always shown wearing the Royal Academy school uniform. She is petite, standing roughly 155 centimeters tall.

Pipi is defined above all by her loyal and devoted nature. She deeply respects Claire, constantly accompanies her around the academy, and tends to agree with everything Claire says, supporting her friend's opinions and decisions without hesitation. She is also protective of her other close friend, Loretta Kugret, and will step in to try to stop people who bully Loretta. Her loyalty can have a harsher edge, however, as she and Loretta are sometimes shown suggesting dark or underhanded schemes to Claire, including bullying tactics aimed at the protagonist Rae Taylor.

Her main motivation is to stay close to and support Claire, and she seems to take her role as Claire's companion seriously. In the larger narrative she functions as part of the background cast surrounding Claire rather than as a driving force in the plot. She receives little attention from Rae, whose focus is fixed entirely on Claire, and her words are rarely taken seriously by the people around her. Because she is a minor character, she does not undergo meaningful development over the course of the series, and the story does not emphasize any notable magical or combat abilities for her. Her value to the series lies mostly in illustrating Claire's inner circle and the environment of noble society at the Royal Academy.