WARGS's collection of info on the ancestry of Camilla gives:
450 Sir John Miller, 4th Baronet, d. 19 Apr 1772 [CB IV:194; Ruvigny Clarence 506]
m. St. Thomas's, Winchester, 31 May 1733
451 Susan Combe, d. 26 June 1788
and
902 Matthew Combe, M.D., of Winchester
m. Droxford, Hampshire, 3 Dec. 1713 [IGI]
903 Susannah ("Hannah") Oglander, b. 1678
http://www.wargs.com/royal/camilla.html
John Vaughan, _Winchester Cathedral: Its Monuments and Memorials_ (London: Selwyn and Blount, 1919), pp. 109-10, provides background on Dr. Matthew Combe of Winchester:
"Several memorials to members of the medical profession may be seen in the north aisle of the nave. Towards the eastern end, I fixed against the wall, is the elaborate marble monument of Matthew Combe , M. D., who died in 1748. It is pyramidal in form, and consists of a funeral urn adorned with flowers, standing on a sarcophagus. Above the urn, which resembles an elegant vase rather than a cinerary vessel, is depicted the Combe coat-of-arms – ermine three lions passant gules – impaling those of the Oglander family – az. a stork between three cross crosslets fitchee or – Matthew Combe having married as his second wife, Hannah, daughter of Sir John Oglander, of Brading, in the Isle of Wight. Matthew Combe was the son of John Combe, of Tisbury, in the county of Wilts, gentleman and was educated at Magdalen Hall, Oxford, where he took his M.D. degree. For the long period of fifty-four years ‘he exercised his art with a singular happiness in the City of Winchester,’ dying at length at the age of eighty-six years. In his earlier career he had the misfortune to lose within a few months of each other his first wife Christiana, and his daughter Finetta, aged sixteen. They lie immediately below the Combe monument, under black stones, with Latin epitaphs of a specially touching character. Mrs. Hannah Combe survived her husband ten years, dying in 1758, at the house now known as Chernocke House, in St. Thomas Street, and was buried in the Cathedral.”
https://babel.hathitrust.org/cgi/pt?id=uc2.ark:/13960/t3bz64p46&view=1up&seq=129&q1=finetta
Since the Combe-Oglander marriage occurred in 1713, and the Combe-Miller marriage in 1733, less than twenty years later, is it possible that Susanna Combe was a daughter of this first wife, Christian, rather than of the second wife, Hannah?