She actually was a face during her debut, when the Corporate Ministry had "abducted" her to have her married with the Undertaker. This was during the whole "greater power" thing where Vince was revealed to be the greater power. This was one of the feuds that made McMahon vs. Austin such a famous and long running angle.
Stephanie originally turned heel when she joined with Triple H (betraying her father in the process, who was then face) during a match with Triple H and she joined DX.
That's when she underwent the wicked transformation from "daddy's little good girl" to a near sexbomb.. don't agree with the implants, but it's all good.
