She decided to tell the woman who hired her that she would begin work as a woman, not a man. Schroer said it seemed as though the woman took the information in stride and that the hiring was going forward as planned.
But the following day, Schroer said she was told that she was no longer "a good fit" for the position. Schroer and her brothers were furious.
With her brothers' encouragement, she filed what many say will become a landmark law suit against the Library of Congress, charging gender discrimination.
She says she's protected under Title VII of the 1964 Civil Rights Act. "She is the same exact person that the Library of Congress knew that they wanted when they first encountered the application. And so there's nothing about that that's changed, except her physical appearance," said American Civil Liberties Union attorney Sharon McGowan, who is representing Schroer.
The Library of Congress first agreed to an interview with "20/20," but then declined, citing Diane's lawsuit. In an e-mail, they wrote that they "acted appropriately and complied with the law" and that "claims such as those raised by Ms. Schroer ... are not covered under Title VII of the Civil Rights Act" or the U.S. Constitution.
While waiting for her day in court and looking for a full-time job, Schroer's deepest fears concerned her family who had yet to see her as a woman. In July, Schroer allowed "20/20" cameras to film her first visit as a sister with her family in suburban Chicago.
The family was understandably surprised by the dramatic change in her appearance, but before long the brothers were reminiscing about their childhood. For Gary and Bill Schroer, the memories are bittersweet as they feel in a sense they've lost a brother while gaining a new sister.
For Schroer, the childhood memories have a far different meaning. She's always known that inside that little boy lived a little girl who longed to grow up and become a woman. "What's great about my life now is that it's unified, it's focused and this huge distraction that was in my life is now gone."