Betsy, or Elizabeth Flanagan is said to be the Virginia Lady who invented the "Cock-tail". This tale may, or may not, be true. For it to be true she must have created the first before 1803 (the current earliest verified reference to the drink Cock-tail). Although if you read the 1853 quote, you might come to the conclusion that Betsy Flanagan invented a drink containing mint, and which would therefore not be a cock-tail, though perhaps it would be a mint sling?
"Works", By James Fenimore Cooper, 1853
"...Betty had the merit of being the inventor of that beverage which is so well known, at the present hour, to all the patriots who make a winter's march between the commercial and political capitals of this great state, and which is distinguished by the name of "cock-tail." Elizabeth Flanagan was peculiarly well qualified, by education and circumstances, to perfect this improvement in liquors, having been literally brought up on its principal ingredient, and having acquired from her Virginian customers the use of mint, from its flavour in a julep to its height of renown in the article in question."