There are 2 titles associated with this person.

@book{ wphp_9069
  author={Johnston,Mary},
  year={1816},
  title={The Lairds of Glenfern;of, Highlanders of the Nineteenth Century. A Tale. In Two Volumes. By Mary Johnston.},
  publisher={Minerva Press, A. K. Newman and Co.},
  address={London},    }
@book{ wphp_9228
  author={Johnston,Mary},
  year={1822},
  title={Domestic Tales; Containing The Merchant's Wife and Her Sister. By Mary Johnston, author of "The Lairds of Glenfern; or, Highlanders of the Nineteenth Century."},
  publisher={G. and W. B. Whittaker \& },
  address={London},    }