I was not aware that Ann Fernell was Nee Burgoyne it explains a lot.
I love looking through old newspapers!

"Yesterday was married Mr William Fernell, of Rotherhith, a Gentleman of large Fortune, to Miss Nancy Burgoyne, of the same place, one of the Co-heiresses of Humphrey Burgoyne, Esq, deceased, a young lady of distinguished Qualifications to make that State happy, with a fortune of 12000 l."
General Advertiser, Friday, December 9, 1748 (and a few other newspapers of the time too)
Modified to add:
Using the National Archives Currency Converter, 12000 pounds is the equivalent of approx 1.4 million pounds, so no wonder she was well qualified!