Ms Clarke was placed in an induced coma due to organ failure and septicaemia, with her sister starting a fundraiser to bring her home for emergency treatment.
'She needs a medivac ASAP as Fiji don't have the medications she needs,' Tam Brown wrote.
Septicaemia is an infection caused by large amounts of bacteria entering the bloodstream.
Ms Clarke died before the medivac crew arrived.
Ms Clarke's brother wrote in a Facebook post on Friday night that the 24-year-old newlywed had gone into cardiac arrest five times within an hour.
'We are so shocked,' he wrote. 'You beautiful girl and amazing sister you will be deeply missed.'
Her husband, Chase Clarke, told Fairfax she was 'outspoken, smart, courageous, and had the biggest heart.'
'Me and Kelly have been through a lot, [she's] been there for me, been my star. I couldn't help her,' he said.
This article originally appeared on New Idea.