Mystery Portrait

At Royal Portraits, this is listed as a painting of Queen Louise of the Belgians, but recently, on a discussion board, I came across a comment to the effect that some think it is a portrait of one of her sisters. I found that quite hard to believe. Only two of her sisters, Marie and Clementine, survived infancy, and both were definitely brunettes:

I thought perhaps it was really that some thought it was a portrait of one of her sisters-in-law, and, in fact, Wikimedia Commons describes the same painting as a portrait of Louise's cousin, Princess Maria Carolina of the Two Sicilies, wife of one of the Belgian queen's younger brothers. If it is Maria Carolina, she looks so much like Louise!