A 19-year-old woman is in a critical condition in hospital after her family say she took a medication overdose.
Cariad Jarrett's family claim she was previously told she was "too young to have depression" by health professionals and was denied the help she needed for her mental health.
They say Cariad was rushed to the Royal Gwent Hospital on Friday, November 1.
She remained in a coma on the intensive care unit for around one week but was transferred when her condition deteriorated, Wales Online reports.
Cariad, who worked as a carer, is now at the Royal Brompton Hospital in Chelsea receiving specialist heart and lung treatment which was not available at the Welsh hospital.
Cariad's sister, Shannon Jarrett, 20, is staying in Kensington, London to be close to her sister along with their parents.
Shannon said a team from the Royal Brompton had to come down to Wales to perform surgery, before taking Cariad to London.
She is currently on a machine which provides cardiac and respiratory support. It is not known how long she will need this machine and doctors are taking it day by day.
"We came down to London to be with her, her situation could change at any time," Shannon said.
"It costs £800 a week to stay in Kensington to be with her and she could be on it for any length of time.
"If we were to go home, it would take us at least three hours to get to her if the hospital gave us a call about her condition. Here, it takes us 20 minutes to walk there."
Cariad and Shannon's father, Dean Jarrett, 45, said their current accommodation arrangements run out on Saturday, November 16.
They are trying to raise money to be able to be by Cariad's side as long as she needs treatment in London.
He said: "We've had an overwhelming amount of support from friends and family.
"But we are yet to find affordable accommodation once this one ends.
"If we were to stay at the hospital's accommodation, we would need two double rooms. This would cost us around £125 a night - it's shocking how expensive it is here."
Shannon set up a GoFundMe page to help support their stay in London, which she described as a "very difficult and emotional time".
