The couple had been holidaying on the South Pacific island in the lead-up to Mr Clarke's best mate's wedding and had conquered a number of phobias together.
The pair were in Sigatoka, Fiji to celebrate their recent wedding, and to attend their friends' wedding ceremony.
The couple had plans to start a family within the next two years. She is in a very unstable condition.
24-year-old Clarke was suffering from extreme pneumonia, which was originally diagnosed as typhoid.
"Kelly was bright, bubbly and over the top; she loved her makeup and always looked the part", Kirribilli Club duty manager Launa Harper said.
Mr Clarke said it would cost $61,000 to fly her body back to Australia in a private plane.
A Department of Foreign Affairs and Trade spokesperson said it was providing consular assistance "to the family of an Australian woman who passed away in Fiji". The diagnosis was only delivered after Kelly passed away on Friday.