Edit - This post crossed with Rosie's post aboveI see from FreeBMD that she was aged 26 when she died. So she was born in 1890/1891.
There are no births of a Constance Steel* in Scotland between 1885 and 1895. However there are three Constance Muriels
Surname Gallie, born Patrick 1889, died Bo'ness 1978
Surname Hines, born Kirkintilloch 1889, no marriage or death in Scotland
Surname Harrison, born Edinburgh 1894, died Uphall 1986
There are two marriages of Constance M Hines in FreeBMD, both after 1917.
There is a marriage of a Constance M Ratcliff to Claude W Steele in Edmonton in 1915, but there is no Constance Muriel Ratcliff(e) in FreeBMD.
There are no relevant births or marriages of a Constance Steel* in Northern Ireland.
There is no Constance Muriel Steel* in the 1911 census index to which I have access. There is just one Constance Steel*, aged 20, born Liverpool, daughter of George Steel, manual training teacher, and Jane Steel both born Liverpool.
This one is the right age, and seems to be the only candidate. However I cannot explain where she acquired a middle name, or why she was buried in Colinton, both of which would seem to rule her out.
I suggest going for the burial record, which should tell you who bought the lair, and who else (if anyone) is buried in the same lair. See
http://www.edinburgh.gov.uk/info/20019/burials_and_cremations/316/burial_records