“Smallville” actress Allison Mack is scheduled to be sentenced on Wednesday after pleading guilty to blackmailing two women as part of NXIVM, a New York-based cult whose leader was convicted of sex trafficking and sentenced to 120 years in prison. Mack, 38, has asked U.S. District Judge Nicholas Garaufis in Brooklyn to spare her prison time and instead sentence her to home confinement or probation. “She cannot undo what has been done, and she will have to live with the regret for the rest of her life,” Mack’s lawyers said in a court filing last week. “But Ms. Mack still holds the potential to be valuable to society—as a family member, as a friend, as a helper to those in need and as a cautionary tale.” Former members testified at NXIVM leader Keith Raniere’s trial that he established a secret sorority within the group in which women were kept on …