When it was announced in late 2010 that Mills - who had her left leg amputated below the knee after a collision with a police motorbike in 1993 - was
attempting to qualify
for the British skiing team at the 2014 Paralympics in Russia, some greeted the news with a degree of scepticism.
A publicity stunt? After two years of extreme learning - including countless broken limbs and ligaments, but also five second-tier race victories - she would argue otherwise.
"I basically said, if I'm going to do this, I'm going to do this properly," Mills, who has bases in Austria and the UK, told BBC Sport.
"Being older is normally a handicap usually as far as physically is concerned, but mentally you tend to be much stronger because you realise that this [being an athlete] is just a privilege."
The 44-year-old spends half of each month training in the Alps. When in England, she endures six-hour round trips from her home to train at the Milton Keynes indoor snow zone.
It is a level of commitment which has impressed many in the British set-up.
"We don't want to take people just to wear the jacket, we are trying to set the standard and achieve a medal, but Heather has every chance,"
chief executive Fiona Young told BBC Sport.
A slippery slope?
Great Britain have
a Winter Paralympic gold medal
GB last attained Paralympic honours on the snow at the 1994 Games in Lillehammer, Norway, where they claimed
five bronze medals
was the highest placed British athlete at the 2010 Vancouver Games, finishing fourth in the Giant Slalom
"Heather is going to find it tough, but she's very focused and also she's in a very privileged position in that she doesn't have to worry about the funding so much."
Following the end of her marriage to McCartney, Mills
received a £24.3m settlement.
She has been able to use these resources to enlist the help of numerous former skiers, including the previous world speed record holder John Clark.
And Mills's journey from recreational skier to one of Paralympic potential would perhaps not have started without a random meeting.
"I was on holiday in Austria, it was really early in the morning and they'd opened the lifts for the racers and one slope was empty so I just kept going straight down," said the charity campaigner.
"I hadn't skied properly for 10 years, but the head of the Slovenian Masters said, 'You know you're doing 100kph (62mph) on slalom skis and that's very dangerous?'
Mills added: "I didn't even know what the skis were because I'd just rented them from the shop, but he said to come and join them."
But despite her impressive speed, Mills's progress was hampered by difficulties with her prosthetic leg, which frequently "ejected" her from her skis.
Mills won four gold medals in the United States in April
In May 2011 she had to be
airlifted to hospital
after colliding with a pole during training and fracturing her shoulder.
Then, just six months later, she injured her partly amputated left leg and broke her thumb.
"I was a little bit concerned because when I went into it [training], the leg kept coming off," said Mills, "but now the London Prosthetics Centre has helped design a new one."
"It means it cuts the circulation off for two minutes from the start to the finish of the course before I release it. But it actually stays on so, fingers crossed, no more injuries!"
As a leg amputee Mills is eligible to compete on a
however due to the metal plates which were inserted into her pelvis after her accident in 1993, medical experts have advised against this move.
It has not significantly hampered her prospects on the slopes, though, as she claimed the Super-G Austria Cup title in the speed race nine months ago.
Four gold medals
followed in April at the US Adaptive Alpine Skiing National Championships in Aspen, Colorado.
"It's not great because I love skiing on one ski. It's so much fun and so much easier, but I've got to do it [compete on two skis] and finally the leg has been sorted," reflected Mills.
"When I won the medals it gave me a lot of confidence - it's brilliant."
The improvements will have to continue throughout the next 16 months if Mills is to attain a place at the Paralympics in March 2014.
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