McDonald was born in 1921, and at the age of 18 acted in the 1939 Australian film "Seven Little Australians" based on the novel by English children's literary writer Ethel Turner she played the twenty-year-old stepmother Esther. She much later appeared in an episode of the 1971 police drama "The Long Arm". The role in Number 96 followed; she reprised the role in the 1974 feature film version of the series. McDonald won several Logie Awards as Best Actress for playing Dorrie, and a Gold Logie for Australia's most popular female personality in 1974. After "Number 96" she played a regular role in the short-lived Australian situation comedy series "The Tea Ladies" (1978).