Daughter of John Cheape. Marianne's first husband was Sir Alexander Campbell of Ardkinglass.
Source The Scots Magazine (August 1792):
"21. At Edinburgh, Sir Alexander Campbell, Bt, to Miss Cheape, only daughter of the late James Cheape, Esq"

Source Hampshire Telegraph (8.10.1810):
"DIED. On the 19th ult. at Dawlish, in Devonshire, Sir Alexander Campbell, Bart. Of Ardkinglass."

Marianne was the third wife of Thomas Bowes Lyon.
Source Perthshire Courier (18.12.1817):
"At Charlotte Square Chapel, Edinburgh, by the Rev. Bishop Sandford, the Hon. Thomas Bowes to Lady Campbell of Ardkinglass."

Source Leith Burghs Pilot (23.6.1900) (extract):
"A NINETEENTH CENTURY INCIDENT OF HOLYROOD.
In 1815 Marianne, daughter of John Cheape, Esq., of Sauchie, and relict of Sir Alexander Campbell, Baronet of Ardkinglass, obtained Royal Warrant to occupy apartments in Holyrood Palace, probably in consequence of being the widow of a Campbell, the Duke of Argyll being hereditary Master of the Royal Household, and having an occasional residence in the Palace. The whole furniture of the apartments belonged to the King, but Lady Campbell brought with her some valuable pictures, probably family portraits.
Her Ladyship afterwards married the Honourable Thomas Lyon or Bowes, as he seems to have been called, his mother being a Bowes and an heiress in her own right. Mr Bowes had already been twice married, having a son and two daughters, all by his first marriage. After the marriage her Ladyship, along with her husband, continued to occupy the apartments at Holyrood…."

Source The Scotsman (27.10.1849):
"At Holyrood Palace, on the 23d inst, the Countess of Strathmore, in the 77th year of her age."

Marianne's brother Captain John Cheape of Girgenti is buried in St Columba's Churchyard in Stewarton.