In 2008, Walsh appeared on the reality television singing competition Rock the Cradle, which featured the offspring of famous Singers competing against one another. She came in third place. Judge Larry Rudolph said that "the hairs on his arms were standing up" after hearing her. She received a "Perfect 10" from Rudolph for her performance of Don Henley's "The Heart of the Matter". Fellow judge Brian L. Friedman said, "Lucy was untouchable ... magical, I was in her soul."
In 2010, Walsh played keyboards for Australian singer Ry Cuming; they toured alongside Maroon 5 and OneRepublic. She has performed at SXSW, the Sundance Film Festival, The Viper Room, Hotel Cafe, and The Hard Rock Cafe in Los Angeles.
In 2012, she filmed roles in the feature film The Truth About Emanuel starring Jessica Biel. In 2013 Walsh shot the horror film No Solicitors opposite Eric Roberts. In 2016, she appeared in the film Mother's Day.