Scarlette

Scarlette, known as Isobel in her youth, (COMIC: Political Animals) was the owner of a brothel on Henrietta Street in the 1780s. Scarlette married the Eighth Doctor as part of a ceremony to bind him with the Earth. (PROSE: The Adventuress of Henrietta Street)

Sabbath once referred to Scarlette as the only woman the Doctor ever got close to. (PROSE: Camera Obscura)

Long before meeting Scarlette, the Eighth Doctor had a vision of "a young woman in a scarlet tunic with long blonde hair" while he was exposed to temporal energies on the Supremacy. (PROSE: Father Time)

Encounter with Faction Paradox
As a girl in 1774, Isobel assisted Snaddon in caring for George III's royal menagerie. When of Faction Paradox caught her eavesdropping on a conversation about the War, she helped her to ride the King's woolly mammoth. (COMIC: Political Animals) After Mayakatula escaped her cell, Isobel confronted her in a church, and Mayakatula taught her the ways of the Mayakai. (COMIC: Bêtes Noires & Dark Horses)

The Babewyn invasion
One of a group who had "inherited" the knowledge of the mysterious elementals following their destruction, Scarlette aided the Eighth Doctor in coordinating a defence against a new danger from outside the conscious universe in 1782, the two actually falling in love to a certain degree over the course of their time together.

Scarlette died shortly after her wedding to the Doctor, in a ceremony that was originally arranged simply to symbolically bind the Doctor to Earth and allow him to participate in its defence, but which, it was implied, developed a deeper meaning for both parties.

According to records, Scarlette faked her death after the crisis was over, recognising that the Doctor's feelings for her would keep him on Earth when he needed to continue travelling to other worlds that would require his help. (PROSE: The Adventuress of Henrietta Street)