Who is Tertius Eileen Anteac from God Emperor of Dune and what is their importance?

With red hair belying her advanced age and a scar of unknown origin on her forehead, Anteac is a Bene Gesserit Truthsayer and covert mentat. She is sent with the younger, more adept Truthsayer Marcus Claire Luyseyal to the Decennial Festival on Arrakis, where the God Emperor Leto II orders them snubbed. When they learn of an assassination attempt against Leto, Anteac is certain the Tleilaxu will boggle it but summons a Fish Speaker guard to tell the story. Anteac is dispatched to see if Face Dancers have infiltrated the Ixian Embassy, and confirms it with a simple "Yes." During an audience with Leto, Anteac opens, asking about Leto's "antics" in the plaza, but then gets down to business.