An Upper East Side woman better learn to stop trashing her ex-husband — or she’s going to forfeit her entire divorce award.

An appeals court has further slashed the $855,000 payout to Janice Schacter, finding that her blabbing about her lawyer-ex’s Playmate girlfriend damaged his business during an economic downturn.

Lower-court Judge Laura Drager had already slashed Schacter’s award from $2.5 million in 2014, reasoning that “the wife chose to bite the hand that fed her” by talking to the press about her estranged husband’s escapades.

Schacter had gone public with claims that her ex, Cadwalader, Wickersham & Taft partner Ira Schacter, bought onetime Playboy model Lace Rose Allenius, 32, a $215,000 diamond engagement ring while refusing to pay for his daughter’s $12,000 hearing aids.

Allenius was a 19-year-old Florida co-ed when she posed nude for Playboy in 2004. Before her engagement to Schacter, she dated actor Matt Dillon for two years.

The former Playboy “co-ed of the week” has said she returned the ring to Ira Schacter after breaking off their engagement.

“I did not break up their marriage,” Allenius told The Post.

“They were already in divorce litigation at the time that I met Ira. We were engaged and I have nothing bad to say about either of them, or Matt Dillon for that matter,” she said.

Ira Schacter, 57, told The Post in 2011, “I love my daughter dearly,” but his attorney insisted Ira didn’t have to pay her medical bills unless he gave prior approval for the care.

The attorney argued that Janice Schacter’s behavior sullied Ira’s reputation and caused him to lose clients to the point that he was dubbed “a–hole lawyer of the month” in 2011 on the Web site Above the Law.

“Her repeated attacks against him have played a part in diminishing his income,” Judge Drager found.

Janice Schacter, 54, had said she was due half the value of her husband’s $5 million partnership at the white-shoe law firm in 2007.

But Drager awarded her just 17 percent, slashing the majority of her share for bad behavior.

Now Manhattan’s appellate division has ruled that Drager, in her calculation, should have used a 2012 valuation for the firm, which was just $1.6 million due to the “financial crisis” and the “negative publicity” generated by the wife’s claims.

The appeals panel ordered a new trial to determine a revised divorce payment to Janice Schacter based on the $1.6 million valuation from 2012, not the $5 million valuation from 2007.

Ira declined to comment. His ex’s lawyer, Thomas Shanahan, blasted the ruling, saying, .“I think it’s going to have a chilling effect, especially on women, to be silent.”