Helen Janet 
WENDLANDT stated in 1914 she had no children however we know she adopted one, her son Franz.  I suggest she also adopted Nella born c1900. I think there would have been birth notices in the Argus if Helen and Bernard had children.  Bernard featured regularly and Helen is also mentioned at functions...including a description of her clothes, which was the norm for that era.   There so few 
WENDLANDT’s in Aus in this period and only one Bernard/t.
http://www.rootschat.com/links/0mdn/WENDLANDT-DOSWELL.-[Silver Wedding.]-On  the 22nd December, 1886 by Pastor Herlitz. German church, Eastern Hill, Bernard Wendlandt, musician, to Helen, daughter of the late 
James Doswell, London. Present address-Kooree, Paradise Valley
The following is speculative research based on the father’s name in the above notice.
The 1886 marriage certificate would be useful but the index states she was born Sussex and there aren’t many 
DOSWELL’s in Sussex.  
1861 Census RG9/587/11/26
Living at Priory Street, Lewes, Sussex
DOSWELL James Head Married 37 years  Engineer in steam packet  Born Romsey, Hampshire
DOSWELL Jane  Wife  Married  26 years  Born Dublin, Ireland
DOSWELL Maria  Dau  6 years  Scholar  Born St Helier, Jersey
DOSWELL Ellen Dau  4 years   Born Newhaven, Sussex
DOSWELL James Son  1 year  Born Southwick, Sussex
I cannot find Ellen on the 1871 but note there was a death of a Jane Maria 
DOSWELL  at Lewes in 1863. ?death of her mother and bearing in mind the 2/3 year gap from the birth of son James, possibly in childbirth.  
Deaths Sep  1863
DOSWELL Jane Maria   Lewes 2b93
Fortunately not many 
DOSWELLS in England…this could be her father 
Deaths June 1876
DOSWELL James  50 years St. Olave 1d152
1881 Census  RG11/445/93/20
Living at The London Hospital,
37 & 38 Alie Street, Whitechapel
DOSWELL Ellen  21 years  Hospital Nurse  Born Newhaven, Sussex
On the 1881 census her elder sister Maria 26 years born St Helier, Jersey Islands is a domestic servant living at  Fenwich Road  Camberwell – so that places her along with her father in London [1911 anniversay notice]
I would suggest this is Maria’s marriage however she is now a tad younger than she should be….
At the Parish Church of St Martin, Kentish Town, Camden
Jun 19 1906  
Henry 
EDWARDS 44 years Bachelor, Decorator of 1 Vicars Road Father Henry Foale EDWARDS decd, gentleman
Maria 
DOSWELL 46 years, Spinster  of 1 Vicars Road  Father 
James Edward DOSWELL, Engineer
Ellen/Helen's age is not constant but her place of birth [Newhaven, 
Sussex] is and the occupation hospital nurse would tie in with her owning a convalescant home in Vic.
1861 born c1857
1881 born c1860
1886 born c1866
1886 Marriage cert....this would be useful.
1914 born c1861
1946 born c1854
An ELLEN DOSWELL  birth was registered in Southhampton in 1845 which matches closely with her age in the trove notification which agrees with her age at death making it highly unlikley that she is Nella's birth mother.
Robyn
I can't find the trove notification that indicates a birth c1845.  She died in 1946 aged 92 years which indicates a birth c1854.  I cannot find a birth registration for Ellen on freebdm and the only registration c1857 in Lewes, Sussex is for an Elizabeth Emily.  Unfortunately people do change their given names 

This appears to be the baptism for the Ellen born 1845 Southampton.
DOSWELL Ellen 
Born 1845
Baptised 8 Oct 1845 at Southampton, Hampshire England
Father 
Richard Doswell  Mother Sarah Sophia
George this will really interest you  
Mercury  Hobart Saturday 22 June 1901
Departures
Warrimoo, s.a., 3,326 tons, H. J. Richardson, for Melbourne. 
Passengers Saloon: 
Madame Wendlandt; 
Misses Turnbull, 
Gill; Mrs. Back; Masters Jamieson, Franz.
Perhaps there were two adopted/fostered daughters.  
For completion on Helen's life.
From arrival in May 1886 - 1914
Lived in
South Yarra 7 months
Moonee Ponds 18 months
Various addresses in City of Melbourne 6/7 years
Brighton 7 years
Paradise Valley 18 years - this would be Menzies Creek
Australian Electoral Roll
1909 already posted
1914
WENDLANDT Helen Janet Menzies Creek  HD
1919, 1924, 1931, 1936, 1937, 1942
WENDLANDT Franz  Clematis   Orchardist
WENDLANDT Helen Janet  Menzies Creek  HD
Helen is buried at 
Emerald Cemetery
WENDLANDT Helen Janet  92 years
Location   H 305  Area   [EM]H-H
I think she was born 1857 and the age on the shipping record should be 30 not 20. The 1861 census is probably the closest to her true age.  
Cheers
Cando