The Seagram liquor heiress Clare Bronfman pleaded guilty on Friday to harboring an undocumented immigrant and enabling credit card fraud as part of an alleged sex cult based in upstate New York, where women have reported they were branded with the initials of the founder.

Bronfman, 40, entered her plea to the two criminal counts before Judge Nicholas Garaufis in federal court in Brooklyn, New York.

She is one of several people charged in connection with a secretive organization called Nxivm, which federal prosecutors have described as a racketeering organization.

Bronfman admitted that she knowingly harbored a woman brought to the United States on a fake work visa in order to obtain that woman’s labor for herself and the organization. She also said she helped Nxivm’s founder, Keith Raniere, use a deceased woman’s credit card.

As part of her plea, Bronfman agreed to forfeit $6m, and not to appeal any prison sentence of 27 months or less. She said she was “truly remorseful”.

“I wanted to do good in the world and help people,” she said. “However, I have made mistakes.”

Bronfman’s lawyer, Mark Geragos, said after the hearing that his client did not have an agreement to cooperate with prosecutors.

Actress Allison Mack, best known for her role on the WB television show Smallville, pleaded guilty earlier this month to blackmailing two women in connection with Nxivm. The former Nxivm president Nancy Salzman and her daughter Lauren Salzman pleaded guilty in March.

Another Nxivm member, Kathy Russell, is expected to plead guilty later on Friday, according to a court calendar. That would leave Raniere as the sole defendant in a trial expected to begin later this month.

Raniere, 58, was arrested on sex trafficking charges in March 2018, and is being held without bail.

Prosecutors accused Raniere of running a cult-like secret society within Nxivm in which women were branded with his initials and forced to have sex with him.

Last month, prosecutors unsealed new charges accusing Raniere of sexually exploiting a minor and coercing her to produce child abuse images.

Raniere has pleaded not guilty. Marc Agnifilo, one of his lawyers, has said that his client’s sexual encounters with women in the organization were consensual, and denied the child abuse images charges.

On its website, Nxivm (pronounced “Nexium”) calls itself “a community guided by humanitarian principles that seek to empower people and answer important questions about what it means to be human”.