She grew up, under her previous, male identity of "Theodore", on a farm during the Great Depression and the New Deal. She was bullied by her father and her brothers, who often told her to "man up" because she preferred reading over things like fighting and baseball.
She eventually ran away to Los Angeles in search of "something different". It was here, in 1939, where she met the Thirteenth Doctor, Yasmin Khan, Ryan Sinclair, and Graham O'Brien. (PROSE: The Wonderful Doctor of Oz)
to be added
Behind the scenes
Dorothy is named after Dorothy Gale, one of the recurring protagonists of L. Frank Baum's Oz books. Notably, the real name of the Seventh Doctor's companion Ace was also a reference to the character, with some details of her life story echoing that of Baum's Dorothy (such as having been propelled from her ordinary life into another world by a "tornado").
Although she is never explicitly confirmed as such in the narrative, Dorothy is very clearly intended to be interpreted as a transgender individual.
Dorothy is the first trans character in the DWU to discover their identity in the course of the story in which they appear, as opposed to already having their identity established as part of their backstory. As a result, Dorothy is referred to throughout the majority of the story by her birth name and with masculine pronouns, before transitioning and switching to feminine pronouns.