Tiffani Amber Thiessen (born January 23, 1974) is an American actress, best known for her roles as Kelly Kapowski in Saved by the Bell and as Valerie Malone in Beverly Hills, 90210. She is also known for starring in Fastlane as Wilhelmina 'Billie' Chambers, as well as for her current role of Elizabeth Burke in the USA Network television series White Collar.