The younger sister of Felix, Ventia (played by Alison Oliver) is something of a “black sheep” in the Catton family as a result of her struggles with mental health. She has a particularly difficult relationship with her mother, Lady Elspeth, who dismisses her struggles as masochism and casually informs others of Venetia’s eating disorder. She becomes close to Oliver at the beginning of the summer, perhaps because of her “outsider” status at Saltburn. However, she dismisses Oliver when she realizes that he, like Felix’s previous friends, prioritizes Felix’s approval over everyone else’s. Felix, she notes, never liked sharing his “toys” even when he grew tired of them. This comment leads Oliver to believe that he will have to fight to keep Felix’s attention and to avoid being dismissed like those who have been invited to Saltburn before.  

Like Farleigh, Venetia seems to understand Oliver better than Felix or Lady Elspeth, correctly perceiving his desire to ingratiate himself with the family. After Felix’s death, she senses Oliver’s clear obsession with Felix, angrily stating that he “ate him right up” and hinting that Oliver has come to Saltburn to destroy her family. Nevertheless, Venetia is, at this point, distraught and heavily medicated and does not act upon her suspicions. In some ways, she shares her family’s elitism despite the uncertain place she holds within the family, treating Farleigh’s desire for financial independence with little sympathy and dismissing Oliver, ultimately, as a mere “serf” and a “moth” trying to make his way into the Catton’s home.