She represented the United States as a junior, but began representing Great Britain in 2010 on joining the senior ranks after moving to England and competed for Great Britain at the 2012 Olympic Games in London.Porter won a bronze medal in the 100 m hurdles at the 2013 World Championships.
In 2014, she won a silver medal representing England at the Commonwealth Games.
Later in 2014 she took her first major title, a gold medal at the European Championships, becoming the first British woman to win a European title in the event.
Her personal best of 12.51 is the current British record.
She is also a two-time medallist over 60 m hurdles at the World Indoor Championships.
She is the sister of Cindy Ofili, another elite-level sprint hurdler with dual British and American nationality; Ofili, too, chose to represent Great Britain internationally.
Unlike Porter, Ofili had never represented the United States as a junior.
Both sisters made the final of the 100 metre hurdles at the 2016 Summer Olympics.