I think you find WW1 Service record at National Australian Archives for Frederick GARDINER - wife Nellie M have been digitised so you can download and read for free.
B2455 GARDINER F Gardiner Frederick : SERN 1007 : POB South Melbourne VIC : POE Melbourne VIC : NOK W Gardiner Nellie M
His married says Fredk Geo GARDENER and Nellie Maria MCDOUGALL 1910.
I think I found the problem - Nellie Maria MCDOUGALL was born Ellen Marion MCDOUGALL in Melbourne 1892 Father: Jno MCDOUGALL Mother Ellen SHANAHAN Her brother Ernest James MCDOUGALL was born Melbourne 1885 Father: John MCDOUGALL Mother: Ellen SHANAHAN Nellie is a common derivative of Ellen and as mother was called Ellen could see daughter receiving nickname. Her brother Ernest James MCDOUGALL was a dentist - you can see his digitise WW1 Service record also online at National Australia Archives.
The Argus (Melbourne, Vic. : 1848 - 1956)(about) Previous issue Thursday 28 June 1883 Next issue MARRIAGES. McDOUGALL—SHANAHAN—On the 20th inst, at Carlton by the Rev. D.M. Maxwell, John Duncan McDougall, late of Kilmore, to Ellen, only daughter of Stephen Shanahan, Esq., Mount William, Kilmore. The Argus (Melbourne, Vic. : 1848 - 1956)(about) Previous issue Wednesday 24 July 1912 Next issue McDOUGALL-On the 22nd July at his residence Wayside Hotel, City road, South Melbourne, John Duncan, the beloved housbane of Ellen McDougall, and loved father of Dr E, J. McDougall, D.D.S. and Mrs, N. Gardner, aged 55 years, (Interred privately Boroondara Cemetery, 23rd inst) Victoria BMD - Jno Duncan McDougall died 1912 (note spelling when searching sometimes you need to try different spelling of names)
If this is helpful let me know and I will see what else I can find.