According to the article in the Buenos Aires Herald, the tiara was a gift from the Dutch "King" in 1951. Besides the fact that the Netherlands had a Queen in those days, it might well be true that Prince Bernhard gave Eva Peron a tiara. Wasn't it an amount of DFl.600.000,- worth the jewelry, he bribed the Argentinians with?
However, it may well be the quality of the photo in Carla's post, but this tiara lacks brilliance and I'm not convinced yet that it isn't a fake one.