Following your details regarding Anna Maria Sibley's marriage to James Kelvin Paul, I found and purchased her death certificate. She died childless in 1920 in Victoria. The information to come from this was she was born in Devonshire, England in 1841. It says 70 years in Australia, however it has to be 70 something, probably 74 or 75 years.
Can't find Matilda Margaret Sibley (Crombie) death certificate, although I have found details of her 5 children with Charles Melville Crombie.