Amanda Lee Quartermaine was born the younger triplet sister of two boys, Teddy and Randy, in 1889, and the last one to survive adulthood. Teddy and Randy both died contacting various diseases in 1891 and 1894 respectively. For some parts of her life, Mandy was technically not in a mental health institution but at a lousy boarding school near what's now called Emmerdale.
Like Mindy before her, she was a combination of sociopath and psychopath, ruthless in nature. As a result, she had contempt and didn't feel empathy for much of her classmates and teachers. Only one teacher, named Mrs Tara Wimbledon, liked her. She became a schoolteacher herself for a few years until leaving the boarding school to start a family.
She left Emmerdale for Coronation street with her favourite classmate (and childhood friend) Eric Lappin in 1914. All of their friends and acquaintances left their hometowns for war. They married in 1916 and gave birth to their only child together, the mostly single Elsie Lappin, in 1919. Both died before Corrie aired its first episode in December 2nd 1960.