Speaking in an interview for Oprah Winfrey's Where Are They Now?, she added: "Hef and I started hitting kind of a rocky patch when it became clear that Bridget and Kendra were leaving, they were moving on to new things.
"I just had enough and just realized all these delusions I'd been under and that this was no longer the life for me."
It's the latest claim Madison has made since leaving the Playboy mansion, after revealing she felt belittled by Hefner, was once called "old, hard and cheap" and considered suicide because she was so unhappy with life in the mansion.
The 35-year-old model admitted she considered drowning herself in the bathtub of the famous house because being Hugh Hefner's No. 1 girlfriend made her so miserable.
Recalling lying in the bath in 2002, she admitted she thought: "If I just put my head under water and take a deep breath in, it would all be over ... Would anyone even miss me?"
Writing in her memoir Down the Rabbit Hole: Curious Adventures and Cautionary Tales of a Former Playboy Bunny, she added: "I just couldn't take my misery anymore.
"Of course my family would be devastated, but I rarely saw them enough for my absence to make a difference...
"Maybe it was the pot and the alcohol, but drowning myself seemed like the logical way to escape the ridiculous life I was leading."
Hefner has spoken about Madison's claims, telling Us Weekly magazine: "Over the course of my life I've had more than my fair share of romantic relationships with wonderful women.
"Many moved on to live happy, healthy and productive lives, and I'm pleased to say remain dear friends today.
"Sadly, there are a few who have chosen to rewrite history in an attempt to stay in the spotlight. I guess, as the old saying goes: You can't win 'em all."
- Bang! Showbiz