King was born on 31 March 1973 in Calista, Western Australia.[2][3] She is the youngest of five children born to Diana Eve Pizer and John Harvie Morris. Her father was born in England and served in the Royal Navy, moving to Australia to work at the Kwinana Oil Refinery. Her mother owned a drapery shop in Rockingham.[4]
King worked as a commercial lawyer in private practice from 1997 to 2005,[3] working in England for a period following her marriage.[5] She then joined UWA's legal department as a research contracts lawyer (2005–2008), later working as chief of staff to the vice-chancellor Alan Robson (2008–2011) and principal advisor of strategic projects (2012–2013). She oversaw the university's centenary celebrations in 2013. Immediately prior to entering parliament she was the chief operating officer of the Perth USAsia Centre, a think tank based at UWA.[3]
In March 2016, King won ALP preselection unopposed for the Division of Brand, following Gray's retirement.[7] She retained the seat for the ALP at the 2016 federal election, increasing the swing to Labor from a nominal 3.7 points to 7.7 points, making Brand one of Labor's safest federal seats in Western Australia.[8] She is a member of the Labor Right faction.[9][10]
In June 2018, King was selected to fill a vacant place on the opposition frontbench, replacing Tim Hammond.[11] She was given the consumer affairs portfolio and also made an assistant minister in the small business and resources portfolios. After the 2019 election she was appointed Shadow Minister for Trade and Shadow Minister for Resources.[3] In March 2021, King stated that the ALP would oppose a moratorium on new coal mines and that "so long as international markets want to buy Australian coal, which is high quality, then they will be able to".[12]
King is married to Jamie King. She has represented Western Australia in Masters (older age) hockey. Her brother is actor John Morris who appeared on Home & Away and Neighbours.[4]