A student who died after catching the flu followed NHS warnings to avoid A&E unless it was an emergency, her family said.
Melissa Whiteley, 18, of Hanford, Stoke-on-Trent, was admitted to Glenfield Hospital, Leicester, on Christmas Day with flu symptoms.
Tests revealed she had sepsis, flu, pneumonia and a fungal throat infection. She died on 27 January.
The NHS said it "would never ask those who need to attend A&E not to go".
Miss Whiteley's family say they want to urge others with similar symptoms to not hesitate to go to A&E.
Her father Mark, 50, said: "She was the happiest person and she had so much to live for."
Melissa's twin Megan told the Stoke Sentinel: "This has broken me, I just don't know what I'll do without her.
"We did everything together. Now that's been taken away from me."
A donation page set up to help cover the cost of Miss Whiteley's funeral has already amassed more than £4,000.
Miss Whiteley was taken to A&E Royal Stoke University Hospital and admitted after six hours. She seemed to be recovering after being given oxygen for several days.
But medics said there was nothing more they could do for her on 29 December and moved her to a specialist unit at Glenfield Hospital.
An NHS spokesman said: "While the NHS is offering extra options for when people feel unwell, the NHS is not - and would never - ask people who need to do so not to go to A&E."
Disease expert Dr David Kirrage, from Public Health England West Midlands confirmed Ms Whiteley died from "flu combined with sepsis".
"This is thankfully very rare, but the loss of someone so young is a tragedy," he said.
In January, the Trust which runs Royal Stoke University Hospital said there had been more than 750 patients admitted with influenza since November 2017, with services "under severe and sustained pressure".