Jessica Taylor suffers debilitating fatigue and painful muscles caused by Chronic Fatigue Syndrome, also known as Myalgic Encephalomyelitis (ME).
The 25-year-old, of Cliffe Woods, Kent, met Samuel Bearman, 24, through friends and they plan to marry next year.
She is working with a physiotherapist in her bid to walk again, and said the wedding would be a "dream come true".
"I've tried to defy doctors. They've given me boundaries and I've tried to extend those boundaries as much as possible," she said.
Mr Bearman said his fiancee was much more than just "someone stuck in a bed".
Ms Taylor added: "There's still a life you can live and it's not wasted years."
Two years ago, with her sister Ruby, Ms Taylor started a charity called Share a Star, which supports sick children who spend their lives indoors.
Last month she was invited to the Houses of Parliament to talk to her local MP, Kelly Tolhurst, about its work.

Imaginative thinking would be required to ensure trade between Northern Ireland and the Republic of Ireland was not affected, said Mr Ahern.
But he believed customs checks were inevitable.
Mr Ahern added that now was not the time for a border poll.
Speaking to the BBC's Today Programme, he said: "There has to be far more consensus, there still is a divided society, the institutions are not operational.
"The big issue, I think, for the Irish and the UK government is on the other side of 8 June is to try to help broker a deal to get the institutions back up and running and certainly having a border poll in the foreseeable future will not help that process."
In March, Mr Ahern told the BBC's Newsnight programme that dissident republicans might use the re-introduction of border posts in Northern Ireland to justify their campaign of violence.
He said a hard border with customs checks would have to be re-introduced because of the UK's decision to leave most of the customs union under Brexit.
Mr Ahern drew a comparison with the IRA's so-called Border Campaign in the 1950s.
But he said he did not expect a return to large-scale violence.
The UK government has pledged to ensure there will be no return to the "hard border" of the past.
A woman is planning to walk down the aisle on her wedding day despite being bed-ridden for almost half her life.
[NEXT_CONCEPT]
Former Taoiseach (Irish prime minister) Bertie Ahern has warned there is no easy solution to resolving the Irish border issue before the UK leaves the EU.