Every source that mentions a goddess mentions Libertas, who was the model for many similar "mascot" designs (Columbia, Marianne, etc). Look at Swiss coinage from the time and see that the female there is very similar to the Statue.

The official word from National Park Services when investigating whether the status was actually of a black female is

"The statue's design almost certainly evolved from an earlier concept Bartholdi proposed for a colossal monument in Egypt, for which the artist used his drawings of Egyptian women as models. Bartholdi’s preliminary design for the Statue of Liberty is consistent with contemporary depictions of Liberty..."

http://www.nps.gov/stli/historyculture/black-statue-of-liberty.htm