She became a protégé of William Pleeth in London and later studied with Harvey Shapiro at the Juilliard school in New York City and with Lynn Harrell in Los Angeles.
In 1999, Forsyth was appointed principal cello of the National Arts Centre Orchestra, a position she left in 2015 to pursue her solo and chamber music career.
She has also collaborated with artists such as Lynn Harrell, Yo-Yo Ma, Garrick Ohlsson, Jon Kimura Parker, Yefim Bronfman, Joseph Kalichstein, Jaime Laredo, Arnold Steinhardt, Michael Tree, and Louis Lortie.
Forsyth is the cellist of the Zukerman Chamber Players, which has toured worldwide since 2003.
In 2007 she also collaborated with Wynton Marsalis in New York, recording the soundtrack for Ken Burns's seven-part television film about World War II for PBS.