Isabel was a harlot in the land of Siron, among the borders of the Lamanites. She is named once in the record, when Alma reproved his son Corianton for forsaking his missionary labors among the Zoramites and going into Siron after her around 74 B.C. (Alma 39:3).
Alma said she “did steal away the hearts of many,” but told Corianton this was no excuse for abandoning the ministry entrusted to him (Alma 39:4). He counted such conduct most abominable above all sins except the shedding of innocent blood and denying the Holy Ghost (Alma 39:5). Alma later warned Corianton not to “suffer the devil to lead away your heart again after those wicked harlots,” explicitly tying her influence to the adversary’s work (Alma 39:11). Corianton’s conduct turned the Zoramites against Alma’s preaching: when they saw what he had done, they would not believe Alma’s words (Alma 39:11).
Isabel is the only individual the Book of Mormon names in this role. Nephi had earlier seen on a cosmic scale the same pattern of hearts being drawn away — the great and abominable church, “the mother of abominations, whose founder is the devil,” exercising dominion over all nations (1 Ne 14:9–11); Isabel’s story at the personal level mirrors that same movement from God toward the adversary.