There are so few DIENER's in South Australia and Vic that I did initially think she may have been a dau of the couple you mention who are buried at Strathalbyn. I did find a letter on TROVE written by Mr H of Strathalbyn and being in the Finnis area I incorrectly assumed it was Edna's father.
I also found a news snippet of Mr H DIENER leaving Parrakie [near Jabuk] for ?Finnis.
Oscar Benno [Peter] gave his address at Marmon Ranges [near Jabuk] on his attestion papers for WW1 however he stated that he wasn't married. His wife was Martha.
It is possible that he is another DIENER who emigrated to Aus with wife Martha, but why can't I find anything for this Henry or Martha after they left the Finnis area.
I wonder if Henry was a witness on Edna's marriage cert?
Perhaps if you have a trawl through the DIENER news items on TROVE you may find something else.
http://trove.nla.gov.au/newspaperCheers
Cando