When did Ann die and did she die in Scotland?  If it was 1855 onwards  downloading a copy of her death cert from Scotlands People will give you her parents names and mothers maiden name
There is an Ann Keard death in 1831 Aberdeen which may be her
See reply below - died in England
From FS
Name    Alexander Keard
Spouse's Name    Ann Gunn
Event Date    08 Mar 1826
Event Place    Saint Nicholas Blotter And Scroll,Aberdeen,Aberdeen,Scotland
Spouse's Father's Name    John Gunn