Mathers described Eminem, 34, as unfaithful and uncaring -- and went as far as to disparage the Grammy winner's sexual prowess.
"I vomit in my mouth whenever I'm around him," she said during the interview on WKQI-FM in Detroit.
Eminem's publicist, Dennis Dennehy, said he had no immediate response to the comments.
Mathers, 31, said she saw the interview as her chance to turn the tables on the rap megastar, who has used his tormented relationship with his high-school sweetheart as a source of his most popular and demented rhymes. He's killed her off in song and assailed her with his lyrics.
Over the past decade, the pair have become one of Detroit's most talked-about couples, thanks to the on-again, off-again nature of the relationship. They also have struggled with substance abuse and have had run-ins with the law.
The relationship hit a new dysfunctional high when Eminem filed divorce papers last April, less than three months after remarrying Mathers. They divorced in December.
Their first marriage ended in 2001. The pair, who have a 10-year-old daughter, Hailie Jade Scott, grew up in the suburbs along Eight Mile Road, Detroit's northern border.
Mathers said Friday that she was "100 percent sure" they never would get back together.
Eminem, whose real name is Marshall Bruce Mathers III, rose to stardom with a number of best-selling CDs, personal lyrics and a starring role in the hit 2002 film "8 Mile."
He has won nine Grammys, including best rap album for "The Slim Shady LP," "The Marshall Mathers LP" and "The Eminem Show." He won an Oscar for the song "Lose Yourself" from "8 Mile."