Housewives rage! LuAnn de Lesseps was incensed by the news that her estranged husband was already engaged to her mortal enemy, Breaking Celebrity News has learned exclusively.

The Real Housewives of New York star and Tom D’Agostino filed for divorce in August, just eight months after they tied the knot but he already popped the question to Anna Rothschild, her former friend, who was spotted wearing a huge diamond ring over the weekend.

“LuAnn is furious about the engagement,” a source told Breaking Celebrity News about the former Countess. “She is just livid over this.”

As Breaking Celebrity News reported exclusively, D’Agostino and Rothschild had lunch at Orsay restaurant in New York City on Sunday, where she was seen with a sparkler on her hand.

De Lesseps’ divorce from D’Agostino was not yet finalized, but was scheduled to happen within 90 days.

“Nothing is going to make this any better, LuAnn is going crazy about this.”

De Lesseps told Andy Cohen she “didn’t see all these red flags” when she was married to D’Agostino.

Calling his behavior “sneaky,” de Lesseps admitted that him meeting up with his ex-girlfriend for drinks behind her back was “the final straw.”

“I had that moment of ‘Oh, my God,’ I had these blinders and all of a sudden they came off,” she said. “I thought, ‘This is not good.’”

Stay with Breaking Celebrity News for updates to the story.