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

Reverend Mother Tamalane is the ghola Duncan Idaho's first teacher on Gammu, Tamalane explains to him the unforgettable pain of a Bene Gesserit punishment. She goes on briefly to become Mother Commander of the Rakian Keep, charged with keeping watch on young Sheeana but is soon replaced by Reverend Mother Darwi Odrade.