O'Callaghan trained as an opera singer after being unable as a teenager to decide whether to become a rockstar or a nun and JazzTimes magazine has labelled her "the stunning Canadian chanteuse with the chilling soprano voice".
[1] Of Irish Catholic heritage, O'Callaghan was born in Dryden, Ontario, and spent her childhood in Iroquois Falls and other northern Canadian towns.
[3] O’Callaghan's first recording, Youkali, was released in 1997 and features cabaret songs by Kurt Weill, Erik Satie and Francis Poulenc.
[5] Another, Jon O’Brien, wrote in a review for the AllMusic website: “A graceful and respectful homage to a true musical icon, Matador: The Songs of Leonard Cohen cements O’Callaghan’s position as one of his most accomplished interpreters.”[6] O’Callaghan was an artist in residence with Soulpepper Theatre Company in the Distillery District of Toronto for six years where she worked "towards her heart's ambition to bring her distinctive brand of cabaret to a broad-based audience".
[7] O'Callaghan was featured as a singing character in the 1999 CBC Television series Foolish Heart and in the 2003 Canadian TV movie Youkali Hotel produced by Enigmatico Films and WestWind Pictures.