How to find my father's sister last known of in Perth Australia?

My father's sister emigrated to Australia sometime in the late 40s early 50s. She first lived in Kalgoorley but was last heard of in Perth. She was married when she left so her name would have been Lila McDowell or MacDowell then, but she was born Caskey. They lost touch many years ago and my father is now almost 79 and would love to know what became of her.