She is portrayed by Jenna Fischer.
Katie is the sister of the film's villains, Stranz and Fairchild Van Waldenberg. They constantly manipulate her into doing their dirty work by telling her that their parents died taking her to skating practice. Her latest task is to spy on the protagonists, Chazz Michaels and Jimmy MacElroy, in order to throw them off track. However, Katie winds up falling in love with Jimmy, which her siblings use to their advantage by threatening to harm Jimmy if she doesn't have sex with Chazz. She attempts to seduce Chazz, but cannot go through with it out of her love for Jimmy. Eventually, she realizes the truth about her parents' death and turns on Stranz and Fairchild, and reconciles with Jimmy.