Miss Mary Conover Lines was born in Mount Vernon, Westchester, New York on 27 July 1895.

She was the daughter of Dr Ernest Howard Lines (1859-1936), a New York native and president and medical director of the New York Life Insurance Company, and Elizabeth Lindsey James (1861-1942), who hailed from Burlington, New Jersey. Her parents had married in Pennsylvania in 1889 and besides Mary they had one other child, a son, Howard Burchard (1892-1916). The family appeared on the 1900 census living in Manhattan. They latterly settled in Paris, where Mary was educated, and they were frequent travellers across the Atlantic.

In April 1912, Mary and her mother were travelling to the United States to attend her brother's graduation from Dartmouth College. They boarded the Titanic at Southampton as first class passengers (joint ticket number 17592 which cost £39, 8s) and occupied cabin D-28.

On Saturday 13 April the two ladies had just finished luncheon in the first class dining room on D Deck. They had made a habit of stopping for coffee in the adjoining reception room following their meal. After they had taken a seat, Captain Smith and Bruce Ismay came and sat at a table nearby and began discussing the possibility of having the last boilers lit. Her mother recognised Mr Ismay from several years back when they had both lived in New York, and she confirmed his identity with her table steward.

On the night of the sinking Mary recalled that she had been dozing off when she and her mother became alarmed when the ship stopped and the noise of steam being vented out could be heard. They were soon pacified by their steward who told them to remain in their cabin which they did, for some time and the steward never returned. Mary later recalled that a man from a neighbouring cabin (whom she identified as a Mr White, possibly Percival White or his son Richard) alerted them to get dressed and helped them find their lifebelts. Half-dressed, the ladies left their cabin and ventured to the boat deck where an officer tied their lifebelts on, saying "We are sending you out as a matter of precaution. We hope you will be back for breakfast."

The two ladies were rescued in lifeboat 9 which Mary described as far from full. When the ship sank, Mary later claimed that she was too far away to hear the cries of those struggling in the water, something she considered a blessing. During sunrise and before their rescue by Carpathia, Mary recalled the magnificent sight of five or six huge icebergs nearby, a scene she would describe as one of the most beautiful spectacles she has ever seen. For Mary, having to climb a rickety rope ladder up the side of the Carpathia was a terrifying ordeal for her and many other survivors in her lifeboat, many of whom were too cold to climb and who had to be hauled up by ropes. Whilst aboard the rescue ship her mother was given a bunk whilst she slept on the floor with another girl around her age.

She and her mother did manage to arrive at her brother's graduation and eventually returned to Paris. During WWI Mary served for four years in a French Hospital as a nurses' aide. Her brother Howard served in the Ambulance Service but died in 1916 as a result of pneumonia.

Mary was married in Paris in 1919 to Massachusetts-born attorney Sargent Holbrook Wellman (b. 8 May 1892) and the freshly-married couple appeared on the 1920 census living with her husband's family in Manhattan but would settle in Topsfield, Massachusetts later that year. The couple had three children: Prudence (1920-1986, later Mrs Joseph Leo Leonard), Howard Lines (1924-2006) and Bradford (b. 1931). The couple were active in their local community in various civic and charitable roles. Mary devoted much of her time to the Girls Scouts on local and national levels since 1923 and was one of the founders of the Mid-Essex area council of Girl Scouts and had served as a commissioner of Massachusetts Girl Scouts for four years, among other roles. She was a member of the Herb Society of America for thirty years, serving as chairman of the New England Unit, and later assisted in the translation of the Natural History of Lavenders from French to English.  

For many years Mary never spoke about her experiences on Titanic and it was not until after the death of her mother that she chose to recount her story. Although invited to the New York premiere of A Night to Remember in 1958, Mary declined the request as she had no wish to relive her experience. She did however speak to local press and did so up until her death.

Mary died at her home, 103 Salem Road, Massachusetts on 23 November 1975 aged 80 following a stroke. She was buried in Pine Grove Cemetery, Topsfield.