Lady Charlotte Elizabeth Bertie was born to Albermarle Bertie, the ninth Earl of Lindsey, and his second wife, Charlotte Susanna Elizabeth (Layard) in 1812. At the age of six, her father died and three years later, when her mother married the Reverend Peter Parsons, Guest began keeping personal journals, a practice that would span seventy years.

The young Lady Charlotte was noted for her intellectual curiosity and, despite her stepfather's efforts to discourage education for girls, she taught herself French and Italian, and studied with her brothers' tutors to learn Greek, Latin, Hebrew, and Persian. Additionally, Guest studied archeology and became well-read in medieval history and legends, which fascinated her.

At the age of twenty-one, she moved to London and met Josiah John Guest, a successful ironmaster and the first Member of Parliament from the town of Merthyr Tydfil, Wales. The couple married on July 29, 1833 and moved into a new mansion built near the Dowlais Iron Company in Merthyr Tydfil. The marriage, a partnership of the upper and the trade class, was deemed scandalous by London's elite, who felt that Charlotte would now be living below her station.

Despite concerns over class difference, the company and community were the shared interests of Charlotte and John Guest. In addition to acting as a company accountant, Charlotte lobbied for her husband's political standing by learning the Welsh language, speaking to local voters, and using her skills as a writer on behalf of her husband. She also worked with John to improve educational standards in the working community. Charlotte visited the schools, teaching occasionally and establishing a system in which teachers trained in London colleges would conduct local classes.

Lady Charlotte Elizabeth Bertie was born to Albermarle Bertie, the ninth Earl of Lindsey, and his second wife, Charlotte Susanna Elizabeth (Layard) in 1812. At the age of six, her father died and three years later, when her mother married the Reverend Peter Parsons, Guest began keeping personal journals, a practice that would span seventy years.

The young Lady Charlotte was noted for her intellectual curiosity and, despite her stepfather's efforts to discourage education for girls, she taught herself French and Italian, and studied with her brothers' tutors to learn Greek, Latin, Hebrew, and Persian. Additionally, Guest studied archeology and became well-read in medieval history and legends, which fascinated her.

At the age of twenty-one, she moved to London and met Josiah John Guest, a successful ironmaster and the first Member of Parliament from the town of Merthyr Tydfil, Wales. The couple married on July 29, 1833 and moved into a new mansion built near the Dowlais Iron Company in Merthyr Tydfil. The marriage, a partnership of the upper and the trade class, was deemed scandalous by London's elite, who felt that Charlotte would now be living below her station.

Despite concerns over class difference, the company and community were the shared interests of Charlotte and John Guest. In addition to acting as a company accountant, Charlotte lobbied for her husband's political standing by learning the Welsh language, speaking to local voters, and using her skills as a writer on behalf of her husband. She also worked with John to improve educational standards in the working community. Charlotte visited the schools, teaching occasionally and establishing a system in which teachers trained in London colleges would conduct local classes. She arranged for celebrated scientists and scholars to provide lectures to the children and helped re-organize the system so those children could remain in school until they were fourteen years of age. Charlotte also founded a school that offered evening classes for men and women, paying close attention to the illiterate girls who had come in from the country to work in the iron industry. The public interests of the community are reflected, also, in John and Charlotte Guest's founding, in conjunction with Lady (Augusta Hall) Llanover, of the Society of Welsh Scholars of Abergavenny. The Society and the popularity of the Welsh festivals, eisteddfods, reflected a growing sense of national history, medieval legend, and Celtic pride, much of which was triggered by the work of James Macpherson and William Owen Pughe.

Although the Mabinogion was widely celebrated in the oral tradition of Ireland, Scotland, and Wales, its stories and significance had been generally overlooked by scholars. In the 1760's, James Macpherson published Ossian, which generated broad interest in Celtic lore throughout Europe and was responsible, in part, for the renewal of interest in medieval literature. Much of that interest, however, came in the form of challenges to Macpherson's claim that the tales originated in the third century. One response was the Myvyrian Archaiology of Wales (1801-1807), a summary of Welsh verse and prose edited by William Owen Pughe. Pughe also authored his Dictionary (1773-1803), a collection designed to assist others in the translation of Welsh prose and verse. Pughe later went on to complete a translation of the Mabinogi, identified as the Mabinogion in his Dictionary; however, the work remained in manuscript due to his death in 1835.

Charlotte Guest used Pughe's Dictionary in her translation of the Mabinogion, but she did not use his translations and, thus, made an original contribution to the Romantic Revival. Encouraged by such scholars as Thomas Price Carnhuanawc, Judge Bosanquet, Villemarqué, and Gwallter Mechain, she completed the undertaking during the period during which she gave birth to her ten children. Her desire to provide her family with a greater sense of their cultural heritage is evidenced in the dedication to her sons, Ivor and Merthyr, in which she states "May you become early imbued with the chivalric and exalted sense of honour, and the fervent patriotism for which its [Wales'] sons have ever been celebrated" (Guest, The Mabinogion). Charlotte worked with Welsh bard, John Jones Tegid, to publish the Mabinogion in 1838-1849, the first successful translation of the famous collection of Celtic tales. Unlike Pughe, Guest emphasized the connection between her husband's cultural heritage and the culture of the continent by giving preference to the translation of the Arthurian tales, Owain, Peredur, and Geraint in her first volume, adding Culhwch and Olwen and Rhonabwy in the second volume. The translations, first published in Llandovery in 1838-1849, brought the tales out of obscurity and fulfilled Charlotte Guest's desire to bring quality medieval Welsh literature to a wider public. Her Mabinogion became the standard translation for almost a century.

At the time of Sir John's death, in 1852, Lady Charlotte took control of the ironworks and carried the company successfully through a period of diminished demand, industry closings, and employee strikes. While maintaining the financial integrity of Dowlais, Lady Charlotte became an advocate for workers who chose not to work on Sunday, supported banning the practice of hiring young women and girls to pile iron at night, advocated an end to distributing pay in public houses, and established a set rate of pay in local industry to prevent further emigration to Australia. When the workers at Dowlais did strike, they returned on terms defined by Lady Charlotte. Only during this period did Lady Charlotte refrain from keeping the journals that she had started at the age of nine.

In 1855, Lady Charlotte married Cambridge scholar, Charles Schreiber, who had joined the household to tutor her son, Ivor, shortly after John's death. Lady Charlotte resumed her journal writing, turned the management of a successful ironworks over to new personnel, and entered into more artistic and literary circles. In addition to members of the aristocracy and the pre-Raphaelites, Lady Charlotte came to know Julia Margaret Cameron and Lord Alfred Tennyson. In her 1877 edition, Charlotte Guest noted that her work provided the basis for the tale of Enid and Geraint in Tennyson's The Idylls of the King.

Lady Charlotte's travels took her, and Charles through Europe and the Middle East. She began seriously collecting china and ceramics and became an established authority on markings and ways to recognize forgeries. In 1884, while in Portugal, Charles died and Charlotte closed that chapter of her life by completing a catalog of their ceramics and presenting the collection to the Victoria and Albert Museum in South Kensington. In the years that followed, she continued to travel, collect, and write, concentrating on antique playing cards and fans. She also remained politically and socially active, working to the benefit of Turkish refugees in the community as well as that of the London cab drivers. In 1887, her personal collection of fans, the first known in history, became the subject of a book she published in conjunction with the Victoria and Albert Museum. She also authored subsequent volumes on English and European fans, respectively, in 1888 and 1891, when she made a gift of her private collection to the Museum.

Lady Charlotte Guest died after a brief illness on January 15, 1895. In keeping with her continual wish to share a piece of history with a wider audience, she bequeathed her final collection, the antique playing cards, to the Victoria and Albert Museum.