Who is Rebecca from Chapterhouse: Dune and what is their importance?

Rebecca is the wild Reverend Mother of the Jews, Rebecca is an older woman in a long, brown gown, hair pulled back, and eyes of total blue with a steely hardness. After undergoing the Agony long ago, she has served "Secret Israel" on Gammu. Her Rabbi, who insists she undertake this assignment, continually kvetches at her for departing from orthodoxy. When the Reverend Mother Lucilla seeks refuge, the Rabbi allows her to Share memories with Rebecca before selling her to the Honored Matres to maintain credibility.