LIBINDX has a listing of Mina K Watson, of 11 Hay Street, Elgin, who died at Spynie Hospital on 27 January 2008 aged 76. The reference is to a death announcement in the Northern Scot. You won't be able to view her birth or death certificates online as they are too recent, or for that matter the 1945 marriage which may or may not be relevant.
If I were you I would go for that 1931 birth certificate. It will tell you the address where she was born, which is probably more useful in working out who she was than where she died.