Her immediate supervisor had been aware of Glenn's condition and was "supportive." But in October 2007, as Glenn prepared to "present 24/7 as the woman she identifies with," her supervisor informed Brumby that Glenn intended to come to work dressed as a woman.
It was shortly thereafter that Brumby summoned Glenn to his office and fired her.
House lawmakers are currently considering the Employment Non-Discrimination Act -- a bill that would make discrimination against gays, lesbians and transgender people explicitly illegal.
"The law really needs to be explicit," Thaler told ABCNews.com. "Otherwise, we have to fight in every jurisdiction from scratch."
The proposed Employment Non-Discrimination Act, H.R. 3017, is similar to federal sex and disability discrimination laws already on the books. It also includes an exemption for faith-based employers.
The Obama administration supports the bill.
But some of its provisions -- like whether to include both sexual orientation and gender identity as protected categories -- have been the center of considerable debate and hindered the bill's progress through Congress.
Some lawmakers question the extensiveness of exemptions for religious schools and other faith-based employers and wonder whether the law, as written, is too nebulous to be enforced.
One group opposed to the legislation, Focus on the Family, says the bill will create a "litigation minefield" and pose a "direct threat to religious liberty in the workplace."
In a letter sent to House lawmakers Sept. 2, the group also said forcing companies to protect against sexual orientation and gender identity discrimination would "harm American businesses" by increasing "compliance costs."
But advocacy groups, like Thaler's organization Lambda Legal, disagree.
"We've had federal sex discrimination laws since 1964 and the Americans with Disabilities Act," said Thaler. "I don't think we've seen any suppression of employers' rights or confusion raining in the courts."
As the debate continues, Glenn, who is currently freelance editing and temping in Atlanta, says she is optimistic about the outcome of her case and broader acceptance of transgender people.
She says she believes her outspokenness is helping to put a human face on the issue.
"It's human nature to fear things we don't understand or know about," she said. "In the past, it was African Americans, Jewish people, even the Irish, at one point. If you don't know about the 'other,' it's easy to demonize the 'other.'"
ABC News' Lisa Chinn contributed to this report.