I was the one to first suggest (on the RJWMB) the idea that the tiara we call the Kent festoon tiara might have originally belonged to Queen Alexandra..
I am firmly convinced by the numerous press reports that Queen Alexandra, as Princess of Wales and later as Queen, had a diamond and pearl tiara. When she became Queen and had access to the Diamond Diadem, which has pearls in the band, it is less easy to distinguish what she may have worn. Nevertheless, I have recently come across a report of her jewels in Berlin 1909 saying that she wore a pearl tipped tiara to a State Ball. Oh for a photo or two!!
Below is a sketch of the State Ball, but it seems to me that the artist was giving only a general impression, but Queen Alexandra is depicted as wearing a tiara similar in shape to the Kent festoon tiara. I am not yet sure how much emphasis to place on the sketch.