The family of only the second person in the UK to have ME recorded on their death certificate say they feel "vindicated" by the ruling.
Merryn Crofts from Rochdale died in May last year, 10 days after her 21st birthday.
Her mother Clare Norton told BBC Radio 5 live's Anna Foster that Merryn had started to doubt herself after being misdiagnosed by doctors.
She said hearing the coroner's verdict "meant everything".
"It's vindication for Merryn because it would have meant so much to her. She was scared of doctors and of telling people she had ME."
Clare described her daughter as a "live wire" growing up, with a packed social life and a love of drama, but said she "lost her bounce" when she started to develop symptoms of ME (myalgic encephalomyelitis), also known chronic fatigue syndrome (CFS), at the age of 15.
"She was like a wind-up toy – when you see the Duracell bunny and the batteries are going.
"If you went for a walk or went shopping, you'd see her deteriorate. Then one day she was at school and she couldn't move her legs, she couldn't stand up."
'What if it is in my head?'
Doctors initially suggested that Merryn was having panic attacks, and her family were later told that she may have conversion disorder, a mental condition formerly known as hysteria.
"I knew it wasn't. I work with people who have panic attacks and I can talk them down," said Clare.
"Merryn was starting to think 'What if it is in my head?' It made her doubt herself, which is awful."
Eventually a private doctor diagnosed Merryn with ME and she began to receive treatment on the NHS.
Within six months of falling ill she was using a wheelchair, and within a year she was housebound.
"She used to say, 'Exhaustion, tiredness, fatigue, I don't care about that, I can cope with that,'" said Clare.
"But she was in a dark room because she couldn't stand the light. She couldn't be touched because her skin was so sensitive. She was in constant pain, different types of pain."
'Like being trapped in your own body'
Merryn's sister Amy described the final three years of her life as "horrendous", adding: "Her hospice doctor likened it to having a heart attack in your stomach."
"The best advice we got was from a doctor who said, 'Whatever you feel you can do, do 50% of that, so you always have energy in reserve.' But in those final years Merryn had no energy in reserve, she was always borrowing from the following day. She never pitied herself, she never wallowed."
Merryn blogged about her condition, writing in 2015: "Having severe ME is like being trapped in your own body every single day. There is no rest, you are bed-bound all day every day.
"It snatches the most simple things away from you like being able to wash yourself, even in bed. Being cared for in every way possible. In terrible pain, from everything."
'Dignity and good grace'
Merryn wrote letters to her family to open after her death. They took her a year to complete as just typing out a few letters at a time left her exhausted.
She has also donated tissue for medical research into ME.
The condition affects around 250,000 people in the UK. It's more common in women and the NHS says it tends to develop between the mid-20s and mid-40s.
Despite its severity, the illness is still not well understood.
The Rochdale coroner, Katherine McKenna, concluded that Merryn's death was due to severe malnutrition caused by the withdrawal of life support nutrition – a condition which was caused by her myalgic encephalomyelitis (ME).
She said ME was "the underlying cause that led to everything" and described Merryn as someone who "bore her suffering with dignity and good grace".
In 2006, the Brighton and Hove coroner ruled that 32-year-old Sophia Mirza died from renal failure as a result of CFS.