According to the grave marker for Narine Grace (Barnum) Mills, she was born in 1880 and died in 1929. Those dates appear to be correct and are noted in this biography.
However, the historical record shows a number of different possible dates and those are also noted here, for the record.
The 1900 Federal Census (enumerated 9 June) recorded 19-year-old Narine Barnum and gave her month and year of birth as Nov 1880. Ancestry.com's Ohio, Births and Christenings Index, 1800-1962, gives Narine's date of birth as 6 Nov 1880. That date of birth was also used in two family trees on Ancestry.com, although the Mills Family Tree gives her date of birth as 6 Nov 1893. On at least one occasion she used the 6 Nov 1893 date, when she was traveling between Hawaii and the Mainland (California, Passenger and Crew Lists, 1882-1959, at Ancestry.com).
In the 1910 Census (enumerated 23 April), Narine was recorded as being 28 years old, which is consistent with the 1880 year of birth recorded in the 1900 Census.
According to Narine and Ernest's Record of Marriage, Territory of Hawaii (Register No. 529), they were married on 9 Oct 1919 in Honolulu. At that time Ernest gave his age as 28 and Narine said she was 34. That's a little closer to the Nov 1880 date of birth that was recorded in the 1900 Census.
Narine's mother, Emma, was 29 years old when Narine was born (1880), and was thus recorded as being 68 years old in the 1920 Census (enumerated February 1920) when she was living with Narine and Ernest in Honolulu. In the 1920 Census Narine gave her age as 32 and Ernest as 29. Following several years of census data, Narine would have been about 38 years old rather than 32.
Narine Grace Mills died on 15 Sep 1929, according to the State of Hawaii Death Index (Reg. No. 1035, Vol. 161).