A 17-year-old girl has died from suspected organ failure two days after going to hospital complaining of shortness of breath.
Maria Titley from Port Talbot, South Wales, had told friends she thought she was suffering from a cough or cold before the sudden tragedy.
Close friend Shaunagh Slattery, 17, said Maria had been due to go out last Saturday night with her girl friends but decided to stay at home because she was feeling unwell.
After going for a check-up at Port Talbot hospital in Neath she was rushed for emergency treatment at the Prince of Wales hospital in Bridgend.
Doctors battled for two days to try and save Maria but sadly she passed away on Tuesday morning.
Sudden: Maria Titley, 17, died on Tuesday after going to hospital complaining of shortness of breath
Miss Slattery said: 'We were all going out on Saturday but Maria said didn't feel well enough to make it.
'She just had bad breathing and chest pains for a few days - she was going to try and shake it off.
'She thought it was something normal, just a chest infection, she phoned up the hospital and went along to get some help with her breathing.
'It just happened so suddenly, no one ever expected this, it's really upsetting how someone can go so quickly.
'It just shows you should cherish the time you have because you never know what's around the corner.'
A talented hockey and netball player, Maria had told friends she felt unwell for around a week.
Miss Slattery added: 'She was such a funny girl, she would brighten up everyone's day.
'She loved life and had so many plans, we were going to go to France next year because she had never been abroad.
Heartbreak: Maria Titley, from Port Talbot, had told friends she couldn't go out on Saturday night because she was feeling unwell
'We were going to go to V Festival too - I'm still going to go and I'm going to take a cardboard cut out of her as a tribute.'
Following the news of her death, Maria's heartbroken school friends gathered at the Port Talbot seafront to release lanterns in tribute to the teenager.
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She was also remembered with a special assembly at St Joseph's Roman Catholic Comprehensive School where she was a pupil in the sixth form.
Headmaster Eugene Scourfield said: 'We are all shocked and saddened by the news of Maria's sudden death and are trying to come to terms with the loss.
'Maria really was a model pupil with an unblemished school record. She was friendly and bubbly and her warm personality and sunny disposition meant that she was popular with staff, peers and pupils of all year groups.
'She was always cheerful and courteous and could light up a room with her smile.'
Maria had been working towards A-levels in Health and Social Care, Sociology and The Welsh Baccalaureate.
Mr Scourfield added: 'She was an excellent role model and a great ambassador for the school.
'She was one of the most dependable and reliable students in the Sixth Form and had participated in many fundraising and charitable events.
Unexplained: Maria Titley had gone to Port Talbot hospital in Neath for a check-up believing she had a cold
Tragic: Doctors at the Princess of Wales Hospital in Bridgend battled for two days to save Maria but sadly she died
'Her death has devastated our school community and we offer our heartfelt condolences to her family.'
Maria's father Dean, mum Cath and sisters Charlene and Jenna were yesterday being comforted by friends and family.
A spokesman for South Wales Police said: 'We are investigating the unexplained death of a 17-year-old girl who died at about 7.40am on Tuesday in a hospital environment.
'The death is not being treated as suspicious. The next of kin and HM Coroner have been informed.'
A spokesman for the Bridgend coroner said he death had been referred to their office.