Yes, difficult to identify but I'm going with the lovers knot tiara. It doesn't look like the Vladimir to me and also I wonder given that the Queen was sitting next to the original owners grand-daughter might it not be a little tactless of her to wear it on this occasion? Yes, she could legitimately wear it but I suspect she would have been a little more tactful given that the events which lead to the sale of the tiara were relatively recent.
--Previous Message-- : : I agree that the pic is a difficult one. : I go for the Vladimir with the drop pearls : hanging forward as her head is bent. :