Sidner began her on-air reporting career at WUFT-TV in Gainesville, Florida. This was followed by periods at KFVS-TV in Cape Girardeau, Missouri, WINK-TV in Fort Myers, Florida, and KDFW-TV in Dallas, Texas. At KDFW, she spent three years as a consumer reporter/anchor. She also distinguished herself by reporting on the Space Shuttle Columbia disaster. In January 2004, Sidner joined KTVU in Oakland, California, where she served as a weekend co-anchor of "KTVU Channel 2 News at 6" and "The Ten O’Clock News". She also served as a weekday reporter for the station.