Tasha Thorne was just 10 when she was diagnosed as a diabetic and 19 when she died last August.
Her mother, Helen Thorne, explained that she had no insulin in her body when she was found.
Because of that, she had developed a complication known as diabetic ketoacidosis, which can be fatal if it is not treated quickly.
And it was not the first time that the family have seen the dangers of diabetes, which often runs in families. Experts say the chances of a child becoming a diabetic are significantly increased if one of their parents has the disease as well.
Ms Thorne said: “Sarah is diabetic herself and I have nearly lost her. She went into a coma when she was eight and the doctor saved her life.”
It is estimated that almost three million people are known to have diabetes in Britain and hundreds of thousands more are thought to have the disease without knowing it.
Tasha, formerly of Anthony Nolan Road, Fairstead, was a former pupil of the Park High School, now the King’s Lynn Academy.
Ms Thorne has also paid tribute to the Nelson’s Journey volunteers who have been supporting Lisa and Sarah since their sister’s death, describing their work as “brilliant.”
She said: “Lisa and Sarah have seen them three times so far and they have been into the school once.”
Based in Norwich, the charity has supported hundreds of children and young people who have suffered a bereavement since it was founded in 1997.
However, the group is wholly reliant on fundraising and donations to continue its work and Ms Thorne said there was a waiting list for appointments.
She said it was a situation that had inspired her daughters to do something for the organisation.
“The Government give no money to Nelson’s Journey at all and the people all work there for nothing. There are lots of children out there that are going through what we’re going through.”
The charity is also holding a purple dinner and dance on April 4 at the Brasteds restaurant in Framingham Pigot, near Norwich.
Ms Thorne has also thanked staff at the Asda store in South Wootton, who will be donating drinks and cakes for the sale at the school next week.