Sean and Marie Devine thought Terri had the flu when she complained of a headache and aches and pains just before Christmas in 2008.
Mrs Devine gave her daughter paracetamol and said there was nothing that made her believe Terri needed medical attention.
But the next day, they found the teenager unconscious in her bed, and she was rushed to Altnagelvin A&E in Londonderry.
Mrs Devine explained: "It was frightening... When we both went to the side of the bed and shook her, there was no response whatsoever - absolutely nothing -I think we both realised then this was really serious."
At the hospital, nurses, who revealed Terri had Meningitis B, brought the couple in to see the schoolgirl before she went for further tests.
Mr Devine said: "It was terrible, I remember walking through the door and there were so many nurses and doctors around her.
"But the thing that sticks in my head was the nurses standing crying, I knew then she was gravely ill."
Two days after she was admitted to hospital, Terri died and her organs were donated to a number of people, including a 10-month-old girl and a 14-year-old boy.
A vaccine has been developed which could prevent more than 70% of meningitis B cases - but it has not yet been given the green light by the government.
What price do you put on a life?
The Devine family have started a petition calling for the injection to be included in the childhood immunisation programme.
"I would feel it an absolute tragedy now if there was a child to die in the next six months, from Meningitis B, knowing that there's a vaccine sitting in a lab that has been licensed," explained Mrs Devine.
"Losing a child is absolutely tragic, but to lose a child where the death might have been prevented and which now can be prevented...
"It will bring contentment to know that hopefully it will not be the case that there is another family having to lose a child."
Other children who have survived Meningitis B have had limbs amputated or been left mentally disabled.
Mr Devine said ensuring other children get the immunisation "would make this project worthwhile".
Almost 13,000 have put their names to the petition which is being backed by the Meningitis Research Foundation.
The vaccine is to be considered by the Joint Committee on Vaccination and Immunisation and a decision expected in June.