Mary was born in Scotland and emmigrated to America in 1900 aboard the Anchor Line's City of Rome. 

She married Daniel Warner Marvin in January 1912. Marvin was the son of a motion picture production house founder and although their marriage ws not actually filmed, it was restaged for the cameras and reported as the first wedding to be "cinematographed". The couple set sail on the Mauretania for a honeymoon across Europe.

They returned on the Titanic in cabin D-30.

As she boarded lifebaot 10, Daniel is reported to have said to her "It's alright, little girl. You go. I will stay." His body was never identified.

Upon return to New York, stricken with grief, she was unaware she had fallen pregnant and gave birth to a daughter, Mary Margaret "Peggy" on 21 October 1912. 

She went on to marry once more, to Horace Silliman DeCamp and had two children. The couple frequently traveleld the Atlantic. Horace died in 1954. 

Mary never spoke about the events on the Titanic, it upset her too much, and she died in New York in 1975.