Boa participated on an upcoming trial hoping to make herself more noticeable to Luffy. However, unlike others who had taken the trial before, her strong willpower allowed her to endure and resist the brainwashing. Nevertheless, the pirate empress was very impressed by how the trial went. Not only did her body became stronger and sexier, the accursed celestial dragon mark on her back had completely removed. Despite the lab's attempt to try and trick her into becoming a mindless drone, she was very pleased with the results.
Thus, Boa struck a deal with the lab. She and the rest of her amazons would be granted free access to the lab and the trials, and in exchange, she will act out as one of their agents. To Boa, these tasks were merely "trainings" to prepare herself for Luffy. She was pretty sure that Luffy wouldn't mind if she gained a little bit of experience.