She was runner-up at the 2018 Volunteers of America LPGA Texas Classic and the 2013 NCAA Division I Women's Golf Championship.

[3] Duncan played collegiate golf at Duke University from 2009 to 2013 where she was a four-time first team All-American, recorded six wins, and was named 2010 ACC Rookie of the Year.

[6] Duncan turned professional in June 2013 after graduating and joined the Symetra Tour, where she recorded three top-10 finishes in seven events in her rookie season.

In 2018, she had her best LPGA season to date, recording three top-10s, including a runner-up finish at the Volunteers of America LPGA Texas Classic, where she birdied her final three holes for a 64, the low round of the tournament, but Park Sung-hyun chipped in on the final hole to win.

[8] In 2023, Duncan recorded a solo third-place finish at the Dana Open and was runner-up at the Inova Mission Inn Resort & Club Championship in one of two Epson Tour starts that season.