The actress, 29, is expecting her first child with her fiance Jason Sudeikis.
"Her" centers on a lonely writer (Joaquin Phoenix), who develops an unlikely relationship with with a new, advanced operating system that's designed to meet his every need.
The film won Best Picture at the Los Angeles Film Critics Awards and was nominated for Best Motion Picture, Musical Or Comedy for the Golden Globe Awards.
"Her" hits theaters on Dec. 18.
Kim looked elegant in a gold satin dress with a matching coat. Her hair, which is naturally dark brown, is currently a blonde ombre, perfectly matching her outfit.
Khloe opted for a white mini dress with long sleeves, while their mother wore a black and white jacket, shiny skirt and boots.
The event honored Winfrey, who was presented with the coveted Sherry Lansing Leadership Award, named after the Hollywood mogul.