I've been stuck with a brickwall for close to 20 years so I understand how you feel Jeanette Lilian Bergoff. In an attempt to help you with yours I've located 65 Lotriet death notices of people who died before 1950..
I did not find a single Johanna Francis on any one of those. The name Johanna Francina/Fransina however appears multiple times. Is it possible that whoever completed the death notice got her name wrong?
I will be adding these DN as I have the time to do so, keep an eye out for all the Johanna Francina/Fransina's, you never know. Something else that I noticed that may assist you in your search is that most of the Lotriet people born around the same time as your Johanna were born in the Carnavon area.