According to her Wikipedia article, Amy Lyon was a very pretty girl born to a blacksmith in Ness near Neston, Cheshire and she wanted out. She left town for London and did work comparable to an exotic dancer today. Fifteen year old Emma Hart, as Amy Lyon had renamed herself, met Sir Harry Featherstonhaugh, who hired her for several months as hostess and entertainer at a lengthy stag party at Sir Harry's Uppark country estate in the South Downs. She is said to have entertained Harry and his friends by dancing naked on the dining room table. Sir Harry took Emma as mistress. She had a child by Sir Harry, after she had met Honourable Charles Francis Greville (1749–1809), second son of the first Earl of Warwick and a member of Parliament for Warwick. She became Greville's mistress. Greville persuaded his uncle, Sir William Hamilton, British Envoy to Naples, to take her off his hands. Sir William was smitten with Emma and, to Greville's shock, married her on 6 September 1791.
Lady Hamilton became a close friend of Queen Maria Carolina, wife of Ferdinand I of Naples. As wife of the British Envoy, Emma welcomed Nelson in 1793, when he came to gather reinforcements against the French. Emma reportedly flung herself upon him in admiration, calling out, "Oh God, is it possible?", as she fainted against him. Nelson wrote effusively of Emma to his increasingly estranged wife, Lady Fanny Nelson. Emma and Sir William escorted Nelson to their home - the Palazzo Sessa. Emma arranged a party with 1,800 guests to celebrate his 40th birthday. They soon fell in love and their affair seems to have been tolerated, and perhaps even encouraged, by the elderly Sir William. She had a girl in 1801, Horatia, with Nelson.
She advised the Queen on how to react to the threats from the French Revolution. Maria Carolina's sister Marie Antoinette had fallen a victim to the Revolution. In 1799 Naples was the scene of a strange revolution, led by members of the aristocracy. The people did not care for the revolution. French troops were welcomed and the royal family fled to Sicily. From here Nelson tried to help the royal family put down the revolutionaries.
Emma spent a year in the company of Horatia before moving to France to try to escape her creditors. Turning to drink, living in poverty in Calais, she died in January 1815 of amoebic dysentery -- an illness she probably contracted during her years in Naples.
Her beauty is detailed in The Judgement of Paris blog that states, "...Emma's allure was so extraordinary that the noted portraitist George Romney was commissioned to capture her beauty on canvas. The moment that he laid eyes on her, Romney was spellbound--so much so, that he spent the rest of his career immortalizing her beauty in one painting after another. The artist 'was patently in love with his model,' Romney's biographer records, but 'it was a worshipful obsession on Romney's part, with Emma, like Dante's Beatrice, as the focus of his inspiration.'
Romney never freed himself of Emma's spell:
'For many years, Romney continued to work on pictures of Emma even after she had left England. In all she sat for him almost 300 times and he made over 50 pictures of her. It was Romney's paintings of her which preserved her image and helped establish her enduring fame. Emma was Romney's muse, stirring him to greater art...' "