Haylie Katherine Duff (born February 19, 1985) is an American actress and singer songwriter. She is best known for being the sister of Hilary Duff and her supporting role on 7th Heaven as well as playing supporting roles in the films Material Girls and Napoleon Dynamite.
Duff was also in a straight to DVD release, Cindy and The Halo Boy, co-starring Frankie Muniz of Malcolm in the Middle fame. In the film, Duff played the leader of a clique of girls in high school who was pregnant with a baby fathered by Muniz's character, nicknamed "Geekling", the leader of a clique of nerdy boys who had wispy mustaches and played the video game "Halo". In summer 2006, Duff joined the Broadway cast of Hairspray, portraying mean girl Amber Von Tussle, and playing the part through the beginning of October 2006. Duff has also starred in Material Girls with her sister Hilary.
Duff is also scheduled to shoot a horror film with Crispin Glover, The I Scream Man.
Duff wrote or co-wrote several songs on three of Hilary Duff's albums, Metamorphosis (2003), Hilary Duff (2004), and the song "Gypsy Woman", on Hilary's fourth album, Dignity (2007). She has recorded numerous singles for various soundtracks with her sister, with most of them appearing on the Disneymania discs. She was featured on legendary rapper Kool G Rap's album Half A Klip, providing the background vocals on the track "On The Rise Again" produced by DJ Premier. She had supposedly completed work on her debut album Walk the Walk due mid 2008. Duff confirmed that this was false; she is not working on or releasing an album at this time.
Duff was involved in a court battle with Paris Hilton over the song Screwed. Both Duff and Hilton had recorded it in 2004, Duff having planned it for her album, and Hilton for it to be released as her debut single, however after what seemed like Hilton had withdrawn from the fight, she was awarded the song by the court, and Duff was left without it. Even though she won the battle for Screwed, Hilton released Stars Are Blind instead, releasing Screwed in Asia only.
As of February 2008, Duff has been seen with Nick Zano.