The Arrow star stunned in a Zuhair Murad dress with simple black Christian Louboutin pumps and a matching patent leather clutch.
The star's rosy blush and lip tint complimented her vibrant lace frock and an elegant top knot finished the stunning look.
Neon lace seemed to be the fete's top fashion theme. Both Holland Roden (in a yellow Marchesa number) and Brittany Snow (in a green Oliver Tolentino Couture sheath) opted for the style.
Yet Katie seemed to reign supreme in the fabric, perhaps partially due to the fact that her see-through frock was a bit sexier than the other similar looks.
What do you think of Katie's look?