Kate wore these long and large earrings to Boujis nightclub in 2007.
Here is the closeup:
It looks like a series of small. overlapping circular golden metal pieces arranged in a drop-down chandelier style. There is a gap between the earring and the hook which appears to be substantial. I would fathom a guess that these are costume jewelry.
I don’t know the maker of Kate’s earrings. I did find a similar looking pair on Belk. They are Erica Lyons Gold Coin Kite Chandelier Pierced Earrings.