Mary Trump, 55, is the daughter of President Trump's eldest brother, Fred Trump Jr, who suffered from alcoholism and who died in 1981 at the age of 42.
In one passage in the book, the president's sister, Maryanne Trump Barry, was allegedly incensed that evangelical Christians started supporting her brother, despite her brother having "no principles."
Asked about the Maryanne Trump Barry passage on Fox News' "Outnumbered Overtime," Conway said the president and his sister have a "great relationship" and noted Maryanne came to the inauguration.
But a New York Supreme Court appellate judge on July 1 overturned part of a lower court decision on the book, ruling that the publisher could move forward with the release of the memoir.
The complaint also claimed that the only exception that would allow Mary Trump to reveal such information would be if Donald Trump, Robert Trump, and their sister, Maryanne Trump Barry, consented.