Watch as she discusses her paranoia and all-consuming addiction.
Then, in August 2008, she was invited to be part of a One Day at a Time reunion on The Rachael Ray Show…but she didn't make it far. On her way to New York City, she was arrested at Los Angeles International Airport for possession of heroin and cocaine.
"That was one of the most terrifying moments of my life," she says. "I cried. I was just weeping. All I could think of was my son. All I could think of was Shane, and God bless him, he is the loveliest person. I'm so lucky to have such a great young man."
Mackenzie was charged with two felony counts of possession of narcotics, and she's serving 18 months of informal probation.
Since her arrest one year ago, Mackenzie says she's been clean.