Katherine got her start modeling for Sears catalogs. She then did commercials, moving onto That Night and King of the Hill. In 1994, Katherine had a main role in My Father, the Hero playing Gerald Depardieu's daughter, she followed that with a role in Under Seige 2: Dark Territory playing Steven Segal's niece. She then starred in the Disney movie Wish Apon a Star. After that Katherine's career took off with appearences on David Letterman and Jay Leno, and the cover of "Seventeen Magazine". Katherine moved to California with her mother after highschool to concentrate on acting full time. She starred in the independant features Prince Valiant and Stand-In's. In 1998, she joined the cast of The Bride of Chucky, starring along side Jennifer Tilly. She then went on to co-star with Peter Fonda in the TV-movie, The Tempest. She played Isabel Evans on the hit UPN show Roswell. Katherine is no longer starring in the hit drama Grey's Anatomy as Isobel "Izzie" Stevens.