Apparently she influenced our language as well:
From W S Penn: "My searching for the origins of gussied up has been noticeably a failure in finding anything other than "origin obscure". It is used for something or someone that is all dressed up or fancy. Anything you have would be appreciated."
Actually, "origin obscure" is a pretty fair summary, but I can put some flesh on the bones.
As you say, something gussied up has been made more attractive, but in a showy or gimmicky way, so it's often not intended to be a compliment. It can also refer to dressing in one's finery for some special occasion, when it is intended to be taken more straightforwardly. It is usually considered to be an American expression, dating from the late 1930s or thereabouts. So it's a little odd that the first recorded use of gussy as a verb in the Oxford English Dictionary comes from a British source, Morris Marple's Public School Slang of 1940, though that doesn't refer explicitly to a verb.
Many people associate the term with more recent events. The American tennis player "Gorgeous Gussie" Moran is best remembered for appearing at Wimbledon in 1949 wearing frilly panties, which caused considerable interest and controversy. Could she have been linked to the phrase? Apart from that odd 1940 example, the first attested use given in the OED and other dictionaries is from 1952, which would fit nicely.
It is possible that the publicity associated with her Wimbledon appearance helped the verb along, and may even have generated gussy up from the existing noun, gussie. But all this is speculation, alas, and we may never know the precise circumstances attached to its invention.