Mills, who is divorcing former Beatle Paul McCartney, says she is appearing on the show for charity, not to gain public sympathy.
"I've been chased and hounded for 10 months and told I'm a publicity-seeker, yet I've never gone out and done anything," the activist and former model says in an interview that was to air Tuesday on the syndicated TV show "Access Hollywood."
Mills, who lost her leg below the knee in a 1993 motorcycle accident, is the first contestant with an artificial limb to compete on the show.
"As much as everyone would love it to go flying, I'm sure it's not going to come off," Mills says. "It can, once it gets hot, start to slide and come off, so I've pulled a sleeve over the top, which doesn't look as cosmetically good."
She adds: "I've got a secondary spare leg just in case I overdo it on the foot and it breaks or something."
McCartney, 64, and Mills, 38, separated last May after four years of marriage and began divorce proceedings in July. They have a 3-year-old daughter, Beatrice.
Mills says she plans to donate her appearance fee to Viva! - an organization that campaigns on behalf of animals killed for food.
"Dancing With the Stars" returns Monday for its fourth season. The new cast also includes Olympic skater Apolo Anton Ohno, model Paulina Porizkova, former "Beverly Hills, 90210" star Ian Ziering, former â€˜N Sync member Joey Fatone and other celebrities.
Mills says her participation on the show is "going to help a lot of kids with disabilities and adults that want to get up and learn to dance, and know that with an artificial leg, you can dance."
ST. LOUIS - Steve McQueen, aka the "King of Cool," will be honored later this month in the central Missouri town of Slater, where he grew up.
McQueen, whose famous movie moments include a mad motorcycle dash in "The Great Escape" and a car chase through the streets of San Francisco in "Bullitt," was born in Beech Grove, Ind., on March 24, 1930. He spent much of his childhood in Slater on his great-uncle's farm, organizers said.
Steve McQueen Days, to be held March 23-25, could help raise the tourism profile of the farming community of 2,100 residents, about 200 miles northwest of St. Louis, the city's assistant administrator, Russell Griffith, said Monday.
"We hope to do it again, but this is a unique opportunity to meet people who knew Steve McQueen throughout his life," said event coordinator Dan Viets, a Columbia lawyer.
McQueen died in 1980 at age 50, having lost his battle against cancer.
The three-day event will include screenings of his movies, a showing of memorabilia and tours to his boyhood home and former school.
Among those expected to attend: McQueen's widow, Barbara McQueen, his stuntman Loren Janes and Pat Johnson, his martial-arts instructor and friend.
McQueen received an Oscar nomination for his role in 1966's "The Sand Pebbles." His screen credits also include "The Magnificent Seven" (1960), "The Great Escape" (1963), "The Cincinnati Kid" (1965), "Bullitt" (1968), "Papillon" (1973) and "The Towering Inferno" (1974).
An auction of McQueen memorabilia from his widow and other collectors in Los Angeles last year brought in $2.9 million. Items included a pair of Persol sunglasses, believed to have been worn by the actor in "The Thomas Crown Affair," which fetched a winning bid of $70,200.