She was the daughter of Henry Bentham (b. 1860) and Mary Jane Smith (b. 1865), both natives of Guernsey in the Channel Islands. She had two siblings: Walter (b. 1886) and Daisy (b. 1888).
Her family appeared on the 1891 Channel Island census living at Tower Lane in St Peter Port, Guernsey. They emigrated later that year and settled in Murray, Orleans, New York where Lillian was born the following year. The family appeared on the 1900 and 1910 census records living in Murray township.
Lillian had been one of a party of 11 visiting the Channel Islands. The group included her godfather William Douton, Peter and Lillian Renouf, Peter McKane, Clifford and Ernest Jefferys, Albert Denbuoy and Emily Rugg. Laurence Gavey may have been one of the 2 others.
Whilst she was away her family moved to Rochester, Monroe, New York.
After the collision on April 14th, 1912 Lillian did not think the Titanic would sink even though she knew that the passengers were being taken off in lifeboats. Only when one of her party, Albert Denbuoy, rushed to her stateroom and told her to hurry on deck did she accept the seriousness of the situation. Miss Bentham was rescued in Lifeboat 12 and she recalled seeing the ship break in two as it sank. Her lifeboat later assisted the men who had managed to stay alive by balancing atop the overturned Collapsible B:
- "I helped the seamen pull those 20 men into our boat, which already had more than 30 in it. We had to pile them on the bottom of the boat, like so many sacks of flour, because they were unable to do anything to help themselves. The boat was very much overloaded when the task was finished."
She would later console a freezing Cecil Fitzpatrick, an Irish crewman rescued from the overturned collapsible. She wrapped her fur coat around the young man, probably saving his life. In gratitude for her help, Cecil gave Lillian a Scout whistle from his belt. He had blown it all night in an effort to call another boat to their aid.
Upon reaching New York aboard Carpathia, her mother could not come to meet her as her brother had contracted Typhoid fever, but eight friends did come, among them the widow of William Douton.
Lillian continued to live with her family in Rochester and appears there on the 1915 census. She was married on 1 September 1917 to John Smellie Black (b. 5 May 1890), a native of Airdrie, Lanarkshire, Scotland but the couple would have no children. They continued to live in Rochester for the rest of their lives and Lillian would later give several interviews in local media regarding her experiences.
Lillian was widowed on June 28th, 1971. She herself passed away on December 15th, 1977.