sI would be interested in what information you do find on the 1953 death certificate. I really think you are wrong to pin your hopes on Samuel Irwin and Ann Jane Johnston are Olive's parents.
It was pointed out earlier that there is a family tree on ancestry with a photograph of Olive M. Irwin's headstone. Other trees show her with a definite death date of 11 November 1948.
Samuel and Ann Jane had a daughter Elizabeth who married under Annie E. Irwin in 1885 Lambton to Richard Boulton. Below is a link to the 1901 census for Eliz. Boulton and her children. Living in the same residence in Lambton County is Ollie Irwin, dressmaker, with a birth date in Dec 1875 - I would think Elizabeth's sister.
http://automatedgenealogy.com/uidlinks/Links.jsp?uid=700233998In 1911 Olive is living with her mother in Ontario
Olive's brother Thomas James Irwin b. Aug 14, 1865 d. 4 Dec 1924. His residence at the time was 234 Napier Street, Sarnia and the informant was his sister Miss Olive Irwin of the same address. Thomas' parents were given as Samuel Irwin Ireland and Annie Jean Johnston Carleton Place.
Another son of Samuel's, John Irwin, d. 1934 in Lambton county and the informant was Miss Irwin of 234 Napier Street.
I would be folliwing the Louisa Irwin b. 7 Mar 1874 London Middlesex ont. to James Irwin and Rebecca Foster. On the 1891 census for London, Ont Rebecca Irwin is a 45 year old widow with son Armon, 23 living with her (he married in 1892 which gave father's name), 17 year old Olive L. (the Louisa of the birth registration? ), and another daughter. Don't see Olive L. Irwin in the 1901 census and in the 1881 for London, Middlesex there is
james Irwin 55 b. Ireland with wife Ann Irwin 45 b. Ire and children John 26, b. Eng , Anthony 24, B. Ont, Mary A. 23, Bridget, 21, George, 18, Lizzie 10, Sarah J. 9, William 7, Louisa 5, Frederick 1.
Added
Not sure if that 1881 is relevant or not. In the 1871 for London James Irwin, 30 and Rebecca 25, have children Annie 5, Armon 3, and Lessie (?) 1. All born Ontario with employment for James shown as oil refinery.
On the 1880 US census for Brooklyn New York a Rebecca Irwin, 34 b. Canada, no marital status indicated, is a niece in the household of Rev. W. W. Clark. His wife Emily and 15 year old son Sherwood were born in Canada.
Debbie