She was the only child of James Reid Watt (1868 - 1937), an architect, and Elizabeth Inglis Milne (1871 - 1951). Her father was born near Aberdeen and her mother in Edinburgh and they had married in 1896.
Bertha first appears on the 1901 census living at 45 Holburn Road, St Machar, Aberdeen. The family were active members of the Belmont Congregational Church and Bertha attended Ashley Road School.
The family decided to settle in Portland, Oregon and James Watt would travel ahead of his wife and daughter, departing from Glasgow aboard the Anchor Line's Caledonia on October 21st, 1911. Mrs Watt and Bertha were originally booked on the New York, but because of the coal strike were transferred to the Titanic. They boarded the ship at Southampton as second class passengers (ticket number C.A. 33595, which cost £15, 15s). On board they shared a cabin with two other ladies, Ellen Toomey and Rosa Pinsky and it seems their social circle included Marion Wright, Kate Buss and William Mellors, with Bertha reportedly developing a crush on the latter. She also befriended eight-year-old Marjorie Collyer.
She was rescued in Lifeboat 9.
Twelve years old at the time, her most vivid memory was that she was roused from her sleep, and told to say her prayers because the Titanic was in trouble. She wrote about the experience as a student in 1917 for the Jefferson High School newspaper in which she claimed the following:
She also recalled the sinking in an interview with the Vancouver Province, in which she spoke of her mother reassuring her that if this were a nice night on Loch Ness you'd just be out for a row, and telling her, "don't worry honey, you weren't born to be drowned, you were born to be hanged."
In 1923 Bertha Watt married a Vancouver doctor, Leslie Marshall, and moved to British Columbia, where she became a Canadian citizen. She and her husband had two sons, James and Robert.
One of her most valuable possessions was the Titanic's second class passenger list. "A day out or so, passengers were given booklets with the names of those in the same class." she said. "My mother had it in the pocket of her tweed coat. When we were picked up by the Carpathia the officers borrowed it to radio the names of the second class passengers to New York."
Although she kept the list in a bank vault, it appears to have been stolen from her. It was not among her possessions when she died in Vancouver on March 4th, 1993.