Here is a Synopsis of the episode
The short synopsis is that LaDonna, the main character of this episode, used to work as an airport tarmac guard. She experienced racial and sexual discrimination, as well as harassment like being forced to work 10+ hours without a bathroom break. Once she was promoted, she witnessed the discrimination first-hand and tried to change the culture from the inside out as the trainer for new hires. Ultimately, she was fired for failing to comply with her supervisor duties... although they never told her she was fired or what the failure was. At one point in the episode, she talks about going to HR with a four-page complaint that referenced policies about discrimination and harassment. They basically told her, "If you can't handle the job, let us know and we'll make you a guard again."
Much of the episode was heartbreaking, and she learned along the way that there had been several previously-settled claims against the company. LaDonna has filed a lawsuit now and works for a different company at the same airport.
The highlighted part is where my point came in. When she was trying to find more people to join the case against her company she found about the settled claims and signed NDAs.