The actress only learned about some things after playing the game.
Recently, actress Jennifer Hale, who voiced the female version of the protagonist in Mass Effect, shared her memories of working on the game.
Most often, the actors read from a script - they learned their lines during the recording:
85% of the time [voice actors] work cold reading [without prior knowledge of the script]. We never see our lines until we go to record; we do a couple of sets of three takes, a few tweaks, and then it goes to market. So when I played Mass Effect, I had a lot more context available to me. I was shocked and thought, "Oh my god, if I had known that, I would have added nuances and that kind of emotion."
Nevertheless, the creators of Mass Effect still provided the actors with certain information - a brief overview of the plot, the world, the development of the characters, an explanation of the branching storylines and dialogue options.
First, Hale recorded a neutral version of the line, and then added nuances for the Renegade and Paragon options:
It was juggling a bunch of details in the moment, but that's what recording for games is like. [Because of this "juggling"] emotional ups and downs are your normal workday. I always joke: Paragon is who I want to be, and Renegade is what I want to say.
