NEW YORK — A New York woman who admitted aiding an ex-convict’s decade-long plot to extort and sexually abuse his daughter’s Sarah Lawrence College schoolmates was sentenced Wednesday to over four years in prison by a judge who called her critical to his scheme.

Isabella Pollok must report to prison by April 25 to begin serving a 4 1/2-year sentence that U.S. District Judge Lewis J. Liman said resulted from her failure to rebel against Lawrence Ray’s crimes.

The judge said Pollok participated in “extreme and sadistic violence” in committing “extremely serious” crimes after being recruited when she was 19 and vulnerable.

“Your role was nonetheless critical,” he said, noting she took steps to prevent a former schoolmate from escaping years of prostitution that produced millions of dollars for Ray. “You were in no means innocent.”

Ray, 63, was sentenced last month to 60 years in prison after his conviction following a trial in which his victims described how he convinced them that they had poisoned him before forcing them to make amends by doing work for him, obeying his commands and paying him cash.

Pollok, who pleaded guilty to a money laundering conspiracy charge last September, stood between her lawyers and sobbed as she briefly spoke before being sentenced.

“I believed and supported someone who controlled me in ways I cannot understand. I will live with the guilt forever,” she said through her tears. “I badly hurt my friends and I am ashamed and deeply regret it. I am truly sorry.”

Pollok, 31, who graduated from the Westchester County school where Ray met most of his victims, faced up to five years in prison.

Her lawyers, who asked that she serve no prison time or receive home detention as an alternative, blamed Ray for manipulating their client after meeting her when she was near-suicidal after a childhood with a mother addicted to drugs and a father and brother in prison.

Liman said the sentence he imposed was in part for Pollok’s cruelty to a woman who Ray had forced into prostitution. The judge said she “gleefully” participated in an assault on the woman in a hotel room where, among other things, she was choked and suffocated with a plastic bag.

Assistant U.S. Attorney Lindsey Keenan said Pollok had played an “active role” in Ray sadistic acts, including handing “him a plastic bag so he could suffocate her college friend.”

Keenan said Pollok also kept a catalogue on her computer of video recordings of her former schoolmates in compromising sexual positions or supposedly admitting they had harmed Ray so she could retrieve the “collateral” if Ray wanted to discipline anyone.

“The next time I see you, you will be in a jumpsuit,” the prosecutor said Pollok once wrote to the woman Ray had forced into prostitution.

Defense attorney David Bertan said Pollok had no lifeline when she met Ray, who brainwashed her.

He noted that the woman forced into prostitution had written to the judge requesting leniency for Pollok.

Bertan said Pollok was rebuilding her life in part by working at an Amazon warehouse.

“I don’t see that a cult victim should have to go to jail for being in a cult,” he said.

Outside court, Bertan said he was disappointed by the sentence.