She was the daughter of Lawrence Mannion and Margaret Small. She had two sisters, Cecilia and Mary.
Margaret bought her ticket at the nearby village of Ballygar and set off for America with a group led by her fiancé Martin Gallagher of Currafurry. Thomas Kilgannon, Thomas Smyth, Margaret and her friend Ellen Mary Mockler were all from the parish of Caltra and were persuaded to come to America by Martin who was visiting his family in Ireland after living in the United States for several years.
She boarded the Titanic at Queenstown as a third class passenger (ticket number 36866, £7 14s 9d).
On the evening of the third day Margaret and Ellen went up for air. It was very cold, and they saw ice and icebergs. They eventually went below.
Of Loughanboy, Ahascragh, County Galway, Mannion left from Queenstown with her fiancé Martin Gallagher, best friend Ellen Mary Mockler and Martin’s two friends, Thomas Kilgannon and Thomas Smyth.
They were getting dressed for bed “when the ship took a very sharp turn which threw both of them to the floor.” At 11.40 PM, just as she was beginning to sleep, there was a sudden, violent jerk which threw people across their cabins. There was silence. The engines stopped.
Margaret jumped up and rushed out into the corridor to see what was going on. So did many of the other passengers. Suddenly, an ear-splitting siren went off and people began to panic. Just then a very loud crashing sound shook the vessel. The two girls were in a terrible state because neither they nor any of the third class passengers knew what was going on .. [they] became desperate when the water started to rise about their feet. The men stormed down the corridors, followed by the ladies in their light clothes. Having smashed a locked barrier, they were face with armed sailors, but they brushed them aside in their frantic desire to get to the boat deck. When they reached the deck, the second class passengers were already climbing into the lifeboats. The sailors had no choice but to let them follow.
Mannion was lucky to jump into the second-to-last boat (No. 16). She could not see any of her friends. She caught a final glimpse of Martin kneeling with a group of passengers on the deck, saying the Rosary. She didn't see Ellen, who was in the same boat.
Martin, Smyth, and Kilgannon all died.
A First Class passenger saved her life by giving her a fur coat to survive in the cold until rescued by the RMS Carpathia.
Upon arrival in New York City where her sister Mary was already living, Margaret became a domestic and lived there for seven years.
In 1919 she returned to her home in Ireland for a visit and married Martin Hopkins there. She spent the rest of her life in the village of Ahascragh where she raised her family, with the exception of the last eleven years when she lived in the town of Clontuskert. She died in Clontuskert, Ireland on May 15th, 1970.