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Your great-grandmother was actually born in 1888. See first link and the fifth record on the page
Her parents were married in 1875 near Spiddal.. See civil marriage record which also shows the names of the fathers of the bride and groom.
Sarah had the following siblings:Patrick 1878 Honor 1880 Daniel 1883 Martin 1885 Michael 1890 James 1894
The family lived in Cloghermore townland in Kilcummin civil parish Here is the 1901 census http://www.census.nationalarchives.ie/pages/1901/Galway/Oughterard/Cloghermore/1394598/
I did not find the family in the 1911 census. Did the entire family emigrate?