It has never been confirmed for sure because of the differences in poses and positioning between the sketches and the final fresco but this is likely just down to the artist's amendments as his work progressed.
The three drawings in question are now stored at the Uffizi, the Ashmolean Museum in Oxford, and the Pinacoteca Ambrosiana in Milan. Indeed the Uffizi has several significant Botticelli drawings whilst the Ashmolean Museum is best known for it's large collection of Raphael drawings.
The female portraiture style is typically Botticelli, simiarities can be drawn with the finished frescos of Primavera and The Birth of Venus - his two most famous works. There are also two other relatively similar drawings in Allegory of Abundance and Angel.
