Who is Muriel from Zami, a New Spelling of My Name and what is their importance?

Muriel is a schizophrenic Italian woman, and one of Audre's lovers. For a time, the women believe they are soul mates, but over time Audre's work and Muriel's mental disorder pulls them apart. Eventually Muriel leaves Audre for another woman, and after a brief adultery incident with one of Audre's ex-friends, Muriel ends up in a hospital program for schizophrenics.