student britt lapthorne , from melbourne , disappeared in 2008 .
she was last seen at a club in the coastal town of dubrovnik in croatia .
her body was found almost three weeks after she disappeared .
she was found badly decomposed in boninovo bay .
croatian police have never solved the mystery of how she died .
her family believes she was murdered and dumped at sea .
a victorian inquest into her death will be closed .