Hi Peter,
I am pretty sure it is Ivy Muriel, not Joy Muriel. It is more obvious on page 7 and the 'I' of the first name is different to the 'J' in Joseph's name.
http://soda.naa.gov.au/record/5823167/1She appears on electoral rolls at Emerald as Ivy Muriel TRELOAR in 1915 and 1916 and on later ones around the Brisbane area as HOLMAN but not at the same address as Joseph. Her death:
1965
B77695
Ivy Muriel HOLMAN
Parents: Harry TRELOAR and Kate COLLINS