I do not see an Elizabeth Douglas on 1861 census for Glengarry but there is an Elizabeth Ross,2yrs.
Same on 1871 census - Elizabeth Ross only.
1881 census www.familysearch.org
She is still with the Ross family but is now listed as 'servant', not daughter, under the name Eliza Douglas, 22, b Ontario.
I did not find an Elizabeth Ross on 1881 census.