Commissioner Joyner, a Democrat, was born in Wadesboro, North Carolina. She attended public schools in Anson County and graduated from West Ansonville High School.. She graduated with high honors from NC A&T State University, Greensboro, with a B.S. in English Education. Joyner became a high school English teacher, working in the public schools of Greensboro and Durham. She left the teaching profession in 1978 to enter the School of Law at the University of North Carolina in Chapel Hill and received her J.D. in 1981. She is a member of the Committee on Consumer Affairs and the Committee on Telecommunications of the National Association of Regulatory Utility Commissioners (NARUC) and a member of the Board of Directors of the National Regulatory Research Institute. Joyner was appointed to the Commission by Governor Mike Easley on January 22, 2001. That term as Commissioner expired on June 30, 2009. She was reappointed by Governor Beverly Perdue for the term that began on July 1, 2009 and ends on June 30, 2017.

Commissioner Joyner has held a variety of positions during her 20 year career as a government lawyer. She served as an Assistant Appellate Defender in the Office of the Appellate Defender from 1981 - 1983. She became a staff lawyer for the Public Staff of the North Carolina Utilities Commission in 1983, and continued her work in public utilities law after joining the Utilities Section of the North Carolina Attorney General's Office. Joyner also served as an adjunct professor at the North Carolina Central University School of Law in Durham. In 1991, she became a Special Deputy Attorney General, supervising the legal assistance provided to the Commissioner and Department of Insurance. She was appointed Section Head of the Insurance Section of the Attorney General's Office in 1995 and managed a full range of legal services provided to several client agencies, including the Department of Insurance, the State Health Plan, the Department of the Secretary of State, the State Auditor, the Department of Commerce, the North Carolina State Ports Authority, and the North Carolina Rural Electrification Authority.

Commissioner Joyner has been active in various bar-related and community service organizations, including the North Carolina Association of Black Lawyers, the Capital City Lawyers Association, the Tenth Judicial Bar, Race Study Circles, and Alpha Kappa Alpha Sorority, Incorporated. She has also served as a member of the Salvation Army Advisory Board and the Board of Directors for HopeLine, Inc., a crisis intervention program.

Joyner is a member of Watts Chapel Baptist Church. She and her husband, Charles, have two children and three grandchildren.