I guess the principle is there. If you look at Adele's IMDb page and then at Léa's one you can understand that a "rising star" needs more than one movie to deserve a nomination for such award. It is not based only on BITWC, but on a group of important works and projects that launch an actor's career and prove his/her talent more than once. Dane DeHaan has done many movies too and imo he's already a star, and the nomination is the same as Léa's. Adèle is a telented actress indeed, but I need more than one movie to judge her acting objectively.