A “kind and generous’’ Long Island mom donated a kidney to save the life of her boss — who then turned around after she got what she wanted and helped fire the poor woman, according to an explosive new legal complaint.

“I decided to become a kidney donor to my boss, and she took my heart,’’ Debbie Stevens, a 47-year-old divorced mother of two, sobbed to The Post.

In papers filed Friday with the state Human Rights commission, Stevens charges that she was clearly set up by Jackie Brucia, 61, her once-ailing boss at the billion-dollar Atlantic Automotive Group, which operates several new-car dealerships.

Stevens said she first got to know Brucia, one of the West Islip company’s controllers, while toiling as a clerical worker for the firm starting in January 2009.

Stevens then left the company in June 2010 to move to Florida. But when she returned to Long Island for a visit that September, she stopped by the office and talked with Brucia, a discussion that included Brucia’s health problems and “her need for a kidney transplant,’’ the papers state.

Stevens told The Post that Brucia told her she’d located a possible donor, a family friend.

But “because she was naturally a kind and generous person, Stevens told Brucia that, if necessary, she would be willing to donate a kidney,’’ the document says.

“Brucia . . . told her, ‘You never know, I may have to take you up on that offer one day,’ ” the papers say.

Soon after, Stevens decided to move back to Long Island for good and asked Brucia if she could return to work there. She had a job with the company again within weeks.

Then, two months later, in January 2011, Stevens told The Post, Brucia “called me into her office and said, ‘My donor was denied. Were you serious when you said that?’ I said, ‘Sure, yeah.’ She was my boss, I respected her. It’s just who I am. I didn’t want her to die.’’

Brucia had been “apparently grooming her to be her ‘backup plan,’ ” according to the papers.

But while Stevens was a close health match for Brucia, she wasn’t a perfect one. So the doctors agreed to allow Stevens to donate her left kidney to someone else in the transplant group so that Brucia could move up the waiting list and get her organ from someone else.

Stevens said she did not realize that she was in for serious pain, discomfort in her legs and digestive problems after the surgery on Aug. 10, 2011. She said she felt pressured to return to work Sept. 6, before she was ready — even while her boss was still recovering at home. When Stevens went home sick three days after her return, she said, Brucia actually called her from home to berate her.

“She . . . said, ‘What are you doing? Why aren’t you at work?’ I told her I didn’t feel good,’’ Stevens told The Post. “She said, ‘You can’t come and go as you please. People are going to think you’re getting special treatment.’ ”

Stevens said that her office and overtime were eventually taken away and that she was demoted to a dealership 50 miles from her home in a high-crime neighborhood that co-workers jokingly called “Siberia.’’ Experiencing mental anguish, she consulted a psychiatrist. and her lawyers wrote a letter to the company — after which Stevens was quickly fired, the papers state.

Brucia did not return phone calls from The Post. She was spotted outside her Babylon home Friday getting into a limo with plastic cups and what appeared to be a bottle of pink champagne.

On Sunday, her husband, James, told a reporter the claims were “far from the truth,’’ but declined to say how. “She didn’t fire anybody,’’ he only said.

AAG also did not return a request for comment.

Stevens’ lawyer, Lenard Leeds, said he plans to file a discrimination lawsuit against AAG, and would likely seek millions of dollars in compensation.

Another lawyer for Stevens, Jason Barbara, added, “[Brucia] turns on her, and she should have been kissing her feet.’’

Still, Stevens said, “I have no regrets [that] I donated a kidney because it saved the life of a man in Missouri.’’

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