The 41-year-old television personality showed her loyalty to Madison after excerpts from the 35-year-old model's tell-all book about Playboy founder Hugh Hefner surfaced. Marquardt, Madison and reality star Kendra Wilkinson were live-in girlfriends to Hefner at the same time.
"I like Holly and I'm friends with her," she told RadarOnline. "I'm happy for her that she wrote the book ... I haven't read [it], so I can't even comment on any of the allegations, but I am definitely going to read it!"
Madison portrayed Hefner in an arguably unflattering light, claiming the CEO offered her drugs and pitted the girlfriends against each other. She also slammed Wilkinson, calling her a "coward" and the "fakest person [she's] ever met."
"I haven't seen or talked to her in years," Marquardt herself said of Wilkinson. "It is crazy. We haven't had a falling out or anything. We just haven't talked. [There's] no reason [for us to ever see each other]."
Madison's book, Down the Rabbit Hole: Curious Adventures and Cautionary Tales of a Former Playboy Bunny, is scheduled for release June 23. Marquardt was Hefner's girlfriend from 2002 to 2008, and went on to marry director Nicholas Carpenter.