Kelly was born into a musical family, with both her parents and sisters being singers. Kelly herself has been singing since the age of seven, when she starred in the musical version of Bugsy Malone. Her parents are both heavily involved in amateur theatre, influencing Kelly toward studying drama, as well as being classically trained in both piano and singing. During her musical career, she has played several principal roles, such as "Velma Kelly" in Chicago, "Florence" in Chess, "Laurie" in Oklahoma, "Maria" in West Side Story, and "Sandy" in Grease.

In addition, Kelly has performed in a number of concerts in Dublin's National Concert Hall, including The Magic of Gershwin, The Music of Cole Porter and From Romberg to Rodgers, and has won numerous national awards for singing and drama.

After deciding to take a break from her day job to return to theatre, she played the lead role in the Christmas Pantomime Jack and the Beanstalk at Dublin's Gaiety Theatre. This led to her being cast in the American production of Riverdance - The Show as lead female vocalist in 2000, a position she held for five years while touring. She also met her husband during this time, who was a dancer for the show.

In 2002, Kelly was asked to record a solo album with director David Downes on the Celtic Collections label. The resulting debut album, Lisa, was released in 2003. She is currently working on a second album. Kelly was again approached by Downes in 2004, and asked to be part of Celtic Woman, originally planned as a one-night event at Dublin's Helix Theatre. The group has since released three albums and embarked on several world tours.

--Wikipedia