The Character, Tulip O’Hare has been cast and will be played by Ruth Negga according to Deadline.com
From Deadline
Agents Of S.H.I.E.L.D.’s Ruth Negga has been cast as the female lead in Preacher, AMC’s drama pilot based on Garth Ennis and Steve Dillon’s cult 1990s comic. The project, from Seth Rogen and Evan Goldberg, is about Jesse Custer, a conflicted Preacher in a small Texas town who merges with a creature that has escaped from heaven and develops the ability to make anyone do anything he says. Along with his ex-girlfriend, Tulip (Negga) — Jesse’s former and only true love — and an Irish vampire named Cassidy, the three embark on a journey to literally find God. Tulip is described as a volatile, action-packed, sexified force of nature, a capable, unrepentant criminal with a love of fashion and ability to construct helicopter-downing bazookas out of coffee cans and corn shine who’s not afraid to steal, kill or corn cob-stab her way out of a bad situation.
Believe it or not, Tulip’s first appearance happened outside of Preacher and was in Vertigo Gallery Dreams & Nightmares #1 1st Tulip O'Hare & Cassidy which can still be found cheap on ebay.