In 2005, she was featured on The Duggans album Rubicon along with peers Moya Brennan and other members of Clannad.
In 2004, Fallon sent a demo offer to composer David Downes, who was then working on the concept of Celtic Woman.
Due to her unique vocal abilities, Downes contacted Fallon and asked if she would like to be a part of Celtic Woman, then only envisaged to be a one-night show.
In 2009, Fallon appeared as a guest vocalist on Jim Brickman's "It's a Beautiful World" tour and PBS special and released her second album Distant Shore (which included her own Shooting Star song) in September of that year.
In this special, as well as Fallon's own songs, there were also songs which featured a few guest singers, including former fellow Celtic Woman member Méav Ní Mhaolchatha, in which they sang a duet together ("Do you hear what I hear"), and American Idol runner up David Archuleta, who joined Fallon on stage to perform "Silent Night", "Patapan", and the finale song of "Here we come A-Wassailing", which Ní Mhaolchatha was also featured in.