[What you need to know to start the day: Get New York Today in your inbox.]

Nancy Salzman was known to her followers as “Prefect.” She was a co-founder of Nxivm, a cultlike group near Albany in which women were branded with the leader’s initials and forced to have sex with him, federal prosecutors say.

On Wednesday, Ms. Salzman pleaded guilty to charges in a federal racketeering indictment filed last year against six people in the group, including the former leader, Keith Raniere.

Mr. Raniere was additionally charged on Wednesday with having a sexual relationship with two underage girls, one of them who was 15 years old when the abuse began.

Ms. Salzman, a former psychiatric nurse, helped Mr. Raniere found the group in the 1990s. In addition to being accused of being part of a criminal enterprise, she was specifically charged with identity theft and altering records to influence the outcome of a lawsuit against the organization.