How did Bibi Andersson contribute to Ingmar Bergman’s group of regular actors?

Bibi Andersson was a key member of Ingmar Bergman's ensemble of actors. After being discovered by Bergman and cast in Smiles of a Summer Night (1955), she went on to portray complex characters in numerous of his films, including Brink of Life (1958) and the critically acclaimed Persona (1966). Andersson also appeared in Bergman's Scenes from a Marriage (1974). Bergman began to assemble a consistent group of actors, including Andersson, with whom he worked regularly, contributing to a distinct style and consistency in his film and stage productions.12