The likelihood is that there is no record of her death. As you'll be aware, statutory registration of births, deaths and marriages did not begin in Scotland until 1855.
Prior to this we are dependant on the parish records (ie the records of the Church). There was no set standard for recording events, and many parishes only recorded deaths if the family had rented a mortcloth.
Have you tried the Monumental Inscriptions of the graveyard in which she is likely to have been buried ?