Ashley played her first match at an ITF event in San Antonio, Texas on 8 January 1996, losing in the second qualifying round to Tu Dong.

Her best Grand Slam result came at the 2004 Wimbledon Championships, where she defeated Tina Pisnik to enter the second round, where she was overpowered by 27th seeded Alicia Molik.

[1] At the Auckland Open held in New Zealand in 2003, Teryn won her only WTA Tour title, playing alongside Abigail Spears to beat Cara Black and Elena Likhovtseva in the final.

Ashley also won the Dow Tennis Classic doubles event with Abigail Spears held 2003 in Midland, Michigan, which was her biggest ITF Women's Circuit title, beating Bethanie Mattek and Shenay Perry in the final.

[2] At the 2002 US Open, Ashley partnered Sarah Taylor to reach the second round of the doubles draw, defeating Laura Montalvo and Elena Tatarkova, 6–4, 4–6, 6–4.