Although the model of the painting is still shrouded in mystery, the landmark exhibition "Leonardo Da Vinci: Painter at the Court of Milan" ( National Gallery of Art in London, 9 Nov 2011- 5 Feb 2012) listed the portrait as possibly depicting Beatrice d'Este, wife of Ludovico Sforza, Duke of Milan. This challenges the portrait's earlier attribution to Lucrezia Crivelli, a mistress of Ludovico.
There are so many confusing references as to who this person was. I think they should just leave her be as the title suggests - Portrait Of An Unknown Woman. " TEXT EXTRACTED FROM: http://jayagandi2010.blogspot.com.es/2012/05/portrait-of-unknown-woman.html