“$10,000 reward given for returned painting,” it read.

The company’s directors, Ian Peck and Terence Doran, responded with a $30 million lawsuit in September in which they accused Ms. Mugrabi of engaging in “an unlawful campaign of intimidation and falsely and maliciously defaming them.”

In an affidavit, Mr. Peck said their company was forced to sell the Warhol for $325,000, a bargain price, to cover its escalating costs and what Peck described as damage to their reputations.

Ms. Mugrabi denies defaming anyone and, undaunted, has countersued. Twice.

“They’re nobody,” she said in a phone interview. “I’m the star, not them, right?”

Art and Acrimony

Ms. Mugrabi is accustomed to the limelight, to legal squabbling and to certain comforts. The daughter of Charles Scher, a plastic surgeon, she grew up “very wealthy,” she once told The New York Times, with homes in Oakhurst, N.J., and Palm Beach, Fla.

She met Mr. Mugrabi, whose art-dealing family owned the world’s largest private collection of Warhols, in Aspen, Colo., in 2001 and married him in New York four years later, at the Pierre hotel, wearing a Victorio y Lucchino gown fitted to her in Spain. The couple, who would have two children, jetted to art fairs in Venice (where they partied on the yacht of the Microsoft co-founder Paul Allen) and vacations in Portofino, Miami and St. Bart’s.

If the marriage was sensational, the divorce was perhaps more so. The precipitating event may or may not have been a 2018 dinner party at the couple’s Hamptons home. Ms. Mugrabi said she woke up in the morning to find her husband and another woman unclothed and asleep beneath a painting by Richard Prince, perhaps after a skinny dip. (Mr. Mugrabi has declined to comment on Ms. Mugrabi’s account.)