Speculation: The new fact that has come to light is that someone from the DNC paid her to make this claim. That would make it a political attack and out any response to it squarely in the official duties category.

“On the basis of information now available with respect to the incidents alleged in the complaint … Defendant Donald J. Trump was acting within the scope of his office as President of the United States at the time of the alleged conduct,” Civil Division Torts Branch Director James Tuohey Jr., said in a certification justifying the move."

https://www.yahoo.com/news/feds-over-defense-libel-suit-024331019.html