Mary started her entertainment career at 15 years of age singing with her brothers, Gerry and the late Spyder Simpson, in the family band called Twilight 5. At the age of 21 she turned professional and sang with Brian Harkin and the Plainsmen, and later with the Times Showband. Mary also performed in many television shows and cabaret throughout  Ireland. Mary has represented Ireland in International song contests in Cavan, Malta, Egypt, Lithuania, Bulgaria and Turkey and won the Maltese International Song Festival and Best Entertainer Award on a number of occasions she also produced her own shows.
 It was while performing in cabaret that she noticed the lack of facilities for children who wanted to perform on stage which led to the founding of the Simpson Stage School in 1993. Since then she has brought joy to hundreds of children through song and dance. Her love of children is particularly evident when teaching in her special needs classes where the children excel because of the personal attention she gives to each child.
Since 2002 Simpson Stage School students have won many competitions and appeared on numerous national television shows because of Mary's dedication and experience in the performing arts. Mary's love of children and music have given her a successful and rewarding career.