Lucy Lintott, 25, was diagnosed in 2013 with MND, aged just 19.
Doctors told her she might have just four years to live, and she feared she might never be a wife.
The inspirational campaigner threw herself into fundraising for charity MND Scotland, so far raising more £200,000 to help find a cure for the debilitating disease.
And she reconnected with now-fiance Tommy Smith, 23, last year, when he did a sponsored head shave for the cause.
The pair - who admit they fancied each other at school - hit it off and last month, welder Tommy got down on one knee to propose at the charity dinner and auction.
An emotional video of the proposal shows Tommy trick Lucy into posing for photos, before he gets down on one knee.
Lucy and Tommy, who only started dating around six months ago, now plan to wed in 2020, and are already busy looking for their dream venue.
Lucy, from Garmouth, Scotland, said: "I feel so much better when he is with me, he is ridiculously caring.
"He makes me forget I have MND and he means the world to me.
"I can't wait to spend the rest of my life with him."
Smitten Tommy added: "Our life has been perfect ever since we met. We couldn't be more similar.
"I could never see myself with anyone else. What's the point in waiting when you just know.
"I asked her dad for permission an hour before I actually did it.
"She told me if she ever got married she wants to have the most sparkly ring possible and I've made sure she gets one.
"I see past her condition. To me it is just Lucy.
"When you love someone as much as I love Lucy you just want to ensure they have a happy life.
"I see her for the person she is. She's amazing and is an inspiration."
Lucy, who is the youngest of three children to mum, Lydia, 56, and dad, Robert, 55, started to feel symptoms of her disease in 2013.She struggled to grip things with her hand and dropped a plate full of food in front of customers while waitressing.
After a visit to the doctors in August 2013, Lucy was referred to see a neurologist, who arranged for an MRI scan and blood test.
Specialists at Glasgow's Queen Elizabeth University Hospital diagnosed Lucy with MND on November 19 2013.
MND is a rare disease, most common in people aged over 40 and develops when nerve cells in the brain and spinal cord progressively and spontaneously lose their function.
It gradually makes gripping, walking, talking and swallowing extremely difficult and eventually impossible.
The disease causes muscles to weaken, stiffen and waste, and will result in Lucy's vital organs failing.
Lucy said: "My body stopped letting me doing what I wanted it to.
"I felt mentally able but I just stopped being able to do some things.
"I sat in a room with my consultant and just explained my symptoms. I was diagnosed a week later.
"They came into a room where I was with my parents. They said they'd ruled everything else out and knew what it was.
"They said it was incurable. I burst into tears and zoned everything else out.
"I was told I might only have three to four years but the doctor said they just don't know."
Since the diagnosis Lucy has raised more than £200,000 to help find a cure, and Tommy heard about her efforts and decided to run Tough Mudder for MND Scotland.
To raise more cash for the upcoming run, he organised a head shave and asked Lucy to do the honours with the clippers.
The pair grew closer in the weeks that followed, before eventually getting together late last year.
Lucy said: "I knew Tommy from school. We were friends for a while.
"We started talking again at a charity head shave. Tommy and his friend were having their heads shaved to raise money for me.
"It felt amazing to know he wanted to help me and we started talking after that. It just went on from there really."
Tommy asked Lucy to marry him at another fundraising event in Stirling, Scotland, on May 17.
She announced the news on Twitter and the post has gained thousands of retweets and likes.
"We were attending a charity event raising money for MND Scotland. I knew he wanted to propose but had no idea when he would do it", said Lucy.
"He said we should go outside to pose for photos but I had no idea we were being filmed.
"He said 'I've got a question for you, will you do me the pleasure of becoming my wife?.
"I said 'no you're not?' I was speechless, I couldn't believe it and found it so surreal.
"I nodded because I couldn't talk. I felt happy, nervous and a bit sick.
"I can't wait to spend the rest of my life with Tommy. My life would be unbearable without him.
"Life without him is just unimaginable.
"It crossed my mind that I may never get married when I was diagnosed.
"He is my best friend and he just has to walk through the door to make me smile."
People with the condition live with it for varying amounts of time after diagnosis and the speed of the disease's progression varies between patients.
Lucy believes that like the famous British scientist Stephen Hawking, she may go on to live a happy and fulfilled life for many years to come.
Lucy has outlived the initial prognosis of her doctors but since 2013, has developed slurred speech and can't walk unaided.
"My disease is progressing extremely slowly," she said.
"I do now have weakness in all four of my joints and I use a wheelchair most of the time.
"I feel extremely lucky in that sense. I felt like my world was crashing down when I first got the news."
Lucy runs her own blog and posts regular updates on her life with MND.
To view Lucy's blog and to find out how to donate to her fundraising page visit www.lucysfight.com.