A possible in 1911 census living in the household of her daughter Mary Donelly.
Sabina Cunningham--82- Kilmanah County Mayo, Ireland
SS
Greenvale,
You wrote that you think ‘Sabina’ and ‘Selina’ are two different people but there doesn’t seem to be evidence of this in censuses.
The one above is with daughter ‘Mary’.
Thomas and ‘Selina’ have daughters, Mary and Margaret.
The children in 1911 look to be the children of Margaret even though 1911 shows Mary.
1901 2844 /112/23
John and Margaret Donnelly
1891 2387/67
John and Margaret Donlan.
Marriage 1886
John Donlan and Margaret Cunningham.
So if this is Selina/Sabina Cunningham, here is Kilmannin which is not too far from Roscommon.
https://www.logainm.ie/en/36377Sorry this is a long way round to confirm 1911 person.