Dave,I have found a marriage of a Elizabeth RILSTONE in the March quarter 1861 in Truro to a William GRUBB I believe it is near Cornwall in england
would this fit with your Elizabeth and her place of birth? I have also found a birth of an Elizabeth RILSTONE in Cornwall with father Samuel and mother Eliza
the marriage was listed on the free BDM english site The birth is listed on the family search (mormon site) if you want to have a look Did Elizabeth come from Cornwall straight to Western australia? The WAbdm indexes are online if you need them to check for births of any children but you probably already have done that Is this all you are after on Elizabeth RILSTONE?