There is a death registration for a David Chester, b. July 15, 1856 London, England, d. April 2, 1922, South Vancouver, BC; married but no spouse's name listed; father is William Chester.
Possibly this is Ruby's father's death.
Just found Louise Chester, age 67, widow, on the same ship as Ruby returning from Australia in August 1926. She lists the same destination (White Lunch, Hastings St.) as Ruby does. Says she was previously in Canada from 1905-1923.
I presume this is Ruby's mother.
Have you checked Australian records for a marriage between Ruby and William there?
Susan