Cathy was 43 years old
First diagnosed with cancer in July 2007, she fought two brain tumours during the next decade.
Cathy played the roles of Meg Bowman on Home and Away and Deborah Hale on The Saddle Club.
Close family friend Sally Browne said: "Cathy was a wonderful, young woman and a very talented young actress.
"But like all brain tumours, it eventually took over and it was just a tragic, tragic end.
"We also had her scrapbooks there and were reading to her - so there were some beautiful, poignant moments as well."
Cathy's death comes just months after her mother, Australian television giant Rosemary Margan, also died on the Gold Coast in December last year at the age of 80.
Rosemary, a champion water skier and three-time Logie winner, was also diagnosed with cancer 17 years prior to her death.
Memorably, Cathy portrayed her mother in the television film The King - which was based on the life of Australian TV great Graham Kennedy.
Our thoughts are with Cathy's friends and family at this difficult time.