Who is Reverend Mother Bellonda from Heretics of Dune and what is their importance?

Reverend Mother Bellonda is an old, fat, florid and vicious Bene Gesserit Archivist, Bellonda opposes the Reverend Mother Superior Alma Mavis Taraza in Council, demanding that the Reverend Mother Darwi Odrade be summarily killed for treason because of her actions on Rakis. No decision is reached. Bellonda insists that the Tyrant would have crushed such a traitor. Bellonda's brief appearance prepares for her substantial role in the next novel, Chapterhouse: Dune.