Nephthys collaborated with River Island for Christmas 2025, designing a festive collection of limited-edition knitwear. The partnership featured playful illustrated jumpers that celebrated seasonal moments with Nephthys' signature style from vibrant Christmas party scenes to festive dachshunds and British holiday icons. The collection gained exceptional press coverage, appearing on popular television shows including "Lorraine" and "This Morning." The designs particularly resonated with fashion media, securing features in leading publications such as Grazia, Stylist, and Glamour magazine. The highly successful collaboration allowed Nephthys to showcase her distinctive illustration work in a fashion context, reaching new audiences and establishing her presence in the retail design space.