During the previous two years her health had deteriorated rapidly. The cystic fibrosis which had made her ill all her life had finally taken hold.
She regularly used a wheelchair, she was on oxygen to help her breathe and was spending longer and longer in hospital.
By that time, Kirstie had met and fallen in love with Stuart.
She had introduced him to her daily dose of medicines, chest infections and hospital visits, all part of the incurable condition's cruel regime.
But soon that regime changed for the worse.
"I had a stair lift fitted and what was once my fitness room, became a dedicated treatment room, full of medicines and devices to help me breathe. I knew we were running out of time""I didn't expect to be so near the edge of life"
Faced with the prospect of little time left together, they planned their wedding in Cyprus only to relocate it to Somerset when Kirstie became too sick to travel.
"We got married three weeks before my transplant. There were numerous medical staff there as well. Stuart had a Do Not Resuscitate card in his pocket because if I had collapsed I did not want to be ventilated, because that would have ruled out a transplant.
"It was the best day of my life but we thought it was going to be my last too."Agony of waiting
Two weeks later she was airlifted to Harefield Hospital in London to wait for a transplant - a last-resort operation which can extend life expectancy but can be very risky too.Kirstie was hooked up to an ECMO machine which imitates the job done by the lungs
Kirstie says waiting for the transplant was the worst time imaginable for her family and new husband.
"At one point I tried to beg them to switch off the machines that were keeping me alive but, because I had a tracheotomy in, no one understood me.
"I was in agony, I felt like I was constantly drowning or suffocating. The number of tubes attached to me was incredible so I couldn't move, couldn't do anything. I felt desperate.
"I didn't think my transplant would come and, if it did, it would surely be too late because I was so weak."
Kirstie wrote an emotional letter to Stuart in case she did not survive.
With her life ebbing away, Kirstie was finally given a new pair of lungs in July 2011.
"It was just in the nick of time," she says. "I had hours left."
But the aftermath of the operation was far from easy. Kirstie still felt very ill when she came round and was still being ventilated.
"I'd had a major operation and it was like starting from scratch again. I thought it was a sick joke. I still felt like I was dying."Return to fitness
Kirstie's new lungs needed time to function fully and properly and that meant constant pain and a steady diet of painkillers for several weeks.Before the transplant: Kirstie with Stuart and comedian Russell Howard on a good day
Intensive rehabilitation got her back on her feet, breathing on her own and with Stuart by her side she knew she would recover.
Her lung function is now at 100%, which Kirstie's doctors are very pleased by.
She maintains that it is down to all the exercise she is doing - six fitness classes a week and three to four hours in the gym - which is key to making the lungs work well.
She is returning to fitness pole dancing and is soon getting back into teaching.
Now she is looking forward to really celebrating Christmas with her family, for the first time in years, and to taking part in a 180-mile charity bike ride.
Yet she is keenly aware that the transplant does not mean she is cured.
"I still won't have the same life expectancy as you, but the transplant will give me maybe 20 more years. I just have to keep managing and controlling the condition as best I can."
In the meantime, Kirstie and Stuart are enjoying the freedom of having her health - and her life - back.