Wheelchair-bound Anne Veasey, 71, died on August 1 last year after she overdosed on a sedative she had bought over the internet.
An inquest heard Mrs Veasey had met someone from a pro-choice website six weeks before taking the fatal dose of the drug she bought online from China.
Speaking after the hearing, her sons Peter and Michael Twyman said: “They told her what she needed to do, how to do it. If someone gives you a loaded gun and then tells you how to use it – are they not culpable?”
The inquest was told the grandmother-of-five was a retired director of a pensions company and a member of Mensa who had taken up the study of quantum physics shortly before her death.
But her health had been deteriorating, she had money worries and had been diagnosed with depression, the court heard.
Mrs Veasey moved into the Bupa-run Southlands Nursing Home in Harrogate in 2009 after the MS affected her mobility.
She spoke about euthanasia with a number of staff, referring to a TV show she had watched, and had researched methods of suicide online as well as reading books such as Dying with Dignity, the inquest heard.
Around six weeks before she died she was visited by a man she told staff was from the website.
Piotr Jania, a care assistant at the nursing home, told the Harrogate hearing she had asked him his thoughts on euthanasia.
A few weeks before she died, Mrs Veasey asked him to help her open a parcel she had received, which contained blister packs of medication and bore either an Arabic or Indian postmark.
Concerned, Mr Jania reported the package, which purported to contain anti-nausea tablets, and her GP was informed.
The court also heard that one day she told him: “I’m losing my mind. MS has finally got me.”
Her distress was added to last spring when social services told her the council would not pay for a large room at the home because she had defaulted on top-up fees.
On July 31, Mrs Veasey asked to go to bed in the late afternoon and was left in her room watching a DVD with a gin and bitter lemon.
She was found the next morning clutching the half-full bottle of gin and a cup with powder was found on the table next to her bed, along with suicide notes.
Detective Constable Ed Noble, who led an investigation into her death, said police had established through emails that she had bought the drug – not prescribed in the UK – online with her card.
Police also found correspondence from Tom Curran, of the website, which revealed he had travelled from Ireland to visit her.
In a voluntary police interview, he said he had not actively encouraged Mrs Veasey to end her own life, but had offered support. No action was taken against him.
Recording a verdict of suicide, Coroner Rob Turnbull said: “It seems to me that she had been making plans for some time that she would end her own life before [the illness] became unbearable.
“She obviously gained some information from that website, not least on what drug she should use to end her life. This was a determined lady and she found a way to obtain this drug.”
Speaking after the hearing, Peter Twyman, 51, said: “This organisation is going around promoting the act of people ending their own lives. It’s abhorrent. My mother still had an active life. To encourage a person in that situation is completely inappropriate.”