In looking at the biography — too late into the 19th century to be the same lady — I had to look up the memoirs of a similarly-named lady. Ah, la Comtesse de Boigne was the Regency-era memoirist! Some of her books are available (free) online.
vol. II: 1815-1819 (US edition)
I have most of the series in its original publication, but several years ago there was a respectable reprint edition.
(all “boigne” books at Archive.org)