(CNN)Imagine traveling down a ski slope at 200km/h (124mp/h.) Now imagine doing so on one leg.
The 47-year-old, who lost her left leg after being hit by a police motorcycle 22 years ago, has set herself the ambitious goal of going over that 200km/h mark in Vars, France, in April.
No female disabled skier has ever attempted the record before, which begs the question why?
"Why not?" Mills flips back quick as a flash with a laugh in a telephone interview with CNN.
The able-bodied female record of 242.59km/h was set by Sweden's Sanna Tidstrand while Australian Michael Milton holds the disability mark with his effort of 213.65km/h set nine years ago.
Mills just relishes breaking new ground for disabled athletes: "With the speed skiing, No.1 I like a challenge and I like to change people's perceptions of disability.
"When I did Dancing with the Stars, no one with a disability had done it. It was the same with Dancing on Ice [in which her prosthetic limb famously flew off mid-routine.] I just like to inspire others."
Hers is a plan originally hatched during a conversation years ago in Australia and further pushed forward more recently by the legendary skier Franz Klammer, with whom she skis in Austria and who has promised her a bottle of schnapps if she is successful. She has also been practicing with the Austrian speed-skiing team.
The record attempt will take her 35 to 50 seconds to complete with a 300-meter stopping area at the finish to allow her to safely come to a halt.
Her team have pored over the safety ramifications of such a stunt and the mother of one says: "If I'm meant to go, I'm meant to go.
"I was in a war zone in Yugoslavia [where she helped victims affected by the Balkan Crisis in 1990 and set up a refugee crisis center in London] and didn't get a scratch. The injuries I've had are from the most mundane things. I was just crossing the road when I got hit by a police motorbike and lost my leg.
"There are dangers, of course of catching an edge but that's not to do with my prosthetic leg -- it's no different to anyone else. And there's the issue of coming back up again at the finish. That's the biggest thing as, if you do that too quickly, it's like a parachute and you'll get yanked backwards hard."
Mills has had a specially designed helmet and outfit for the record attempt but underneath it all will oil her entire body: "I'll be covered in lubricant between the skin and me. I know it makes me sound like some sort of dominatrix! But if I slide down the mountain, it's not going to rip me to shreds."
The window for the record has been set between April 4 and 17 although much depends on the weather, Mills understandably needing sufficient snow as well as clear and still conditions for such a venture.
Despite the risks, she is adamant there is no danger of her leg breaking having had a specially designed hydraulic leg created solely for the rigors of such an attempt.
Having performed on the British television series The Jump -- in which celebrities tackle ski jumping -- with a prosthetic leg, she is adamant her latest adventure foray holds no fears for her.
So what would it mean should she hit that 200km/h barrier, which speed skiers have told her makes a sound like Concorde in full flight?
"The record would be out of this world. It's against all the odds, apparently it's not really possible but it challenges people's perceptions. Everything is possible if you focus on it and train for it."
For now, her record plans have gone relatively under the radar, unlike her every move when married to McCartney. The couple divorced in 2008 but Mills was vilified in the British press, branded "Lady Mucca."
Why is that? "Anyone that married John [Lennon] or Paul got slated or abused [by the press.] It destroys people's lives. So there's this perception now.
"When I did The Jump, the crew came up to me and said 'oh my God, when we heard you were going to be on the show we thought you were going to be really difficult' but they said I was the most laid back. It's just there were so many lies out there."
Mills also claims that being a strong woman has counted against her and, the fall-out from a litany of stories, made her realize who her friends are.
Of the better known names, she says Hillary Clinton and Richard Branson were among the few to stand by her.
And in her latest venture she is particularly emboldened by the support of 11-year-old daughter Beatrice, who Mills says is "proud and excited for her Mummy to be a world record holder and believes she can do anything."
The record is merely another obstacle and such obstacles, she says, have made her more determined to succeed.
Looking back on her life-changing accident, she recalls: "Losing my leg was not so hard, it was the crushed pelvis that was harder. I just thought 'this has happened' and I wasn't going to let it stop me."
Skiing has been a big part of that although, in the early days, there were some comedic mishaps on the slopes with less sophisticated prosthesis.
"I remember skiing when I hit this ice rock and I twisted my knee and snapped by thumb," she adds. "I fell and two 17-year-olds came to see if I was okay. All they could see was my leg dangling and coming off. The leg had turned around like Worzel Gummidge's head. They went white."
Such mishaps are a thing of the past and Mills is confident she will stay in one piece and on track to break the 200km/h mark, the same speed as someone free falling out of a plane.