Nicole Kidman considered this a passion project for years, and she at one point considered to direct herself, following difficulties with finding a director. However, in 2014 she decided to let go off the project.
Charlize Theron was the first choice for Gerda Wegener but dropped out. Her role was then given to Gwyneth Paltrow, who also dropped out in order to spend more time with her family. Marion Cotillard was considered too. The role was then given to Rachel Weisz who also dropped out soon after.
The true origin of Gerda Wegener (Gerda Gottlieb Wegener Porta (15 March 1886 - 28 July 1940)) is Danish, not American. The novelist changed her origin to American to suit the American readers. Not to be confused with German makeup artist Gerda Wegener.