'Donald's nightmare': Mary Trump drops insider info on what gets under her uncle's skin

Donald Trump's niece dropped some insider information on her uncle on Friday, revealing to the world what the former president will be hurt by most from the civil fraud case he's facing.

Trump, who went on a social media posting spree targeting New York Attorney General Letitia James presumably after learning that she had asked for more than $100 million in additional damages in the fraud case, lashed out at James Friday. He said, "They should pay me!"

But Mary Trump says the media missed the biggest part of the story in terms of its potential impact on her uncle.

"While everyone is focused on Letitia James’ request in court today, I will provide some analysis and also a very big piece of information that the corporate media is missing," she wrote.

ALSO READ: 'You lost Ivanka': Trump the target of bogus political action committees

She also claimed it's not the additional funds, but the request to stop doing business in the New York real estate industry that will really get his goat.

"Knowing Donald as I do, I know that it’s the second request by Letitia James that will really get under his skin," Mary Trump wrote, citing James' filing urging Judge Engoron to bar Trump from New York real estate for life. "Donald spent his entire adult life creating an image that he was a real estate genius at the top of his game. This was his obsession and a fantasy, built entirely on the back of my grandfather’s success, a lifetime of lies and bank loans, and Mark Burnett’s tragic decision to center the Celebrity Apprentice around a failed businessman."

Now, according to Mary Trump, his "house of cards is about to collapse."

All that might be pushing Trump to face some tough decisions, according to Mary.

"While a possible $370 million fine and a lifetime New York real estate ban would rock Donald’s world, there is one very realistic outcome that could send set Donald on the brink of ruin: being forced to sell Mar-a-Lago," she wrote. "For that possibility, I spoke with attorney Joe Gallina who told me just how likely that scenario really is."

Gallina, according to Mary Trump, said simply, "the answer is yes."

Regarding what will happen with Mar-a-Lago, Mary Trump adds: "I have some ideas about how the property can be repurposed—and I’m throwing a party. Are you coming?"