The daughter of “Dynasty” actress Catherine Oxenberg spent a year on a 500-calorie-a-day diet while in Nxivm’s secret sex cult, a former slave testified Friday.

Ex-member “Nicole” testified that “Smallville” actress and alleged slave master Allison Mack was so manipulative, she’d threaten to starve Oxenberg’s daughter India even further to ensure that Nicole remained obedient.

”When India and I became close, they would use her to make me behave,” Nicole explained during the sex-trafficking trial of accused Nxivm leader Keith Raniere.

“Alison was trying to have [Oxenberg] get down to a certain weight, and they decided that goal weight was 107 pounds,” Nicole said.

Previous witnesses have described how Raniere preferred his “slaves” skinny, sleep-deprived and compliant.

“It was just really hard to watch, sometimes,” Nicole sobbed as she recalled seeing Oxenberg struggle with her forced diet. “It was tough on her.”

Even when Nicole finally gathered the courage to leave the group, Mack tried to lure her back in, again using her friend.

“The first thing Allison said is ‘Look what this is doing to India, she hasn’t eaten since she got your email,” Nicole testified of her final meeting with her fellow slaves. “And India said ‘Well, that’s not entirely true.'”

The 31-year-old actress repeatedly broke down Friday as she described the humiliating rituals she endured for her “master” Mack — including weekly naked group pictures for Raniere that the former Smallville sidekick termed “family photos.”

The svelte brunette told jurors she knew the photos were for Raniere because she’d seen him respond to a texted image from Mack, writing “all mine” alongside a devil emoji.

“This was supposed to be a a woman’s empowerment group, how is it empowering to make us take off our clothes to send photos to a man?” she sobbed to jurors.

“How is it empowering? Because it feels completely degrading.”

Nicole testified she met with her fellow slaves at least once a week at Mack’s Halfmoon, New York home for what the actress called “church service.” Mack had nicknames for all her slaves, Nicole told jurors, saying the onetime TV star called her “the Brat,” and Oxenberg “the Princess.”

The DOS slave’s mother and father wept from the gallery as she described the excruciating pain of having Raniere’s initials seared into her flesh with a cauterizing pen.

“I was resigned to the fact that I was getting branded,” Nicole said, and then broke down again as she explained that she focused on thoughts of her family as she endured the ordeal.

“It sounds stupid now, but I thought, ‘What would you go through for your little brother?’ And I thought, ‘I can do this. I can do this.'”

She said she finally felt free to leave after coming across a blog run by a Nxivm defector that listed her as a sex slave of Raniere’s.

“It was like, a flash of reality,” she said.

When she finally confronted Raniere, he told her DOS was a walk in the park, she testified Friday.

“You guys think you have it so bad,” she recalled him saying. “But this is nothing compared to other alternative subculture groups.”

Nicole, whose last name is being withheld, continues on the stand in Brooklyn Federal Court on Monday.