Who is Sheeana Brugh from Heretics of Dune and what is their importance?

Sheeana Brugh is a Fremen child born on the planet Rakis, Sheeana is collecting melange in the desert when a worm penetrates the water defenses and swallows her village. She rides the worm to Keen, where the Rakian priests take her in, awed at her seeming ability to control the giant worms, whom they worship as Shai-Hulud, but she insists on calling Shaitan. The Bene Gesserit has long awaited a "Sandrider," and begins keeping tabs on Sheeana. The priests are divided in their opinions about her, with the High Priest Hadley Tuek revering her but others wanting to test her.