The Racing Calender records Mrs. Thornton as the only woman to have ridden in a flat race. On the 24th August 1804 she raced against her brother-in-law Capt. Flint. This first public challenge, which she lost, was rumoured to have attracted 100,000 spectators. A bitter argument ensued concerning the 1000 gns stake. This ended with Flint attacking Mrs. Thornton's husband with a whip. The following year, in her last recorded race, she defeated by half a neck the renowned jockey Mr. F. Buckle