The sculptor was said to have denied that any human model had been used.
I have heard it said that the inspiration for the lady holding the torch, whether the sculptor was conscious of it or not, was Delacroix's painting of "Liberty Leading the People" painted in 1830 and now hanging in the Louvre. Construction of the Statue began in France in 1875 so Bartholdi would certainly have known of Delacroix's painting at that time. And the formal title of the Statue, "Liberty Enlightening the World", personifies "Liberty" just as Delacroix's painting did. Have you seen "Liberty" in Delacroix's painting? Her right arm holds the French Tricolor aloft just as the Lady of Ellis Island holds the torch of freedom aloft. Please visit this link and judge the resemblance for yourself?
http://www.ibiblio.org/wm/paint/auth/delacroix/liberte/