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 Gerard Depardieu's daughter, she followed that with a role in Under Siege 2: Dark Territory playing Steven Seagal's niece. She then starred in the Disney movie Wish Upon a Star. After that Katherine's career took off with appearances on David Letterman and Jay Leno, and the cover of Seventeen Magazine. Katherine moved to California with her mother after high school to concentrate on acting full time. She starred in the independent features Prince Valiant and Stand-In's. In 1998, she joined the cast of The Bride of Chucky, starring alongside 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 Izzie Stevens.