[2] Following success at junior level, she competed at the Queensland Championships several times, winning on four occasions (1935, 1937, 1939 and 1940).

Also in 1939, Hardcastle, in partnership with Emily Hood Westacott, reached the final of the women's doubles of the Australian Championships, losing to duo Thelma Coyne and Nancye Wynne.

Additionally, she won the 1938–39 edition of the ladies' singles and mixed doubles at the New Zealand Championships.

[3] In the early 1940s, during the Second World War, Hardcastle enlisted to the Australian Army Medical Women's Service.

She later joined efforts at Morotai before transferring back to Australia upon the end of the war.