Ugh, this is my absolute favorite scene featuring Paige because it’s so symbolic. It was too hard not to notice and take something from it the moment I first saw this episode (such is the life of a photographer though).
The light is vulnerability and it’s far too much for her to begin with so she has to shrink away to the state she worked so hard for: the distant, aloof commander who would never dare to let anyone cross her. She takes a step back and settles in the comfortable darkness where nobody can reach her — especially Beck — because she’s not willing to show the side of her she wishes she could show.
She can create task forces, she can easily strategize plans to take down the Renegade, recognize patterns to create harmonies, but allowing herself to connect with another Program is something that cannot be put into an orderly box like everything else in her life is. It’s something she is not yet ready to face.
Like Tron, she let friendship (with both Quorra/Ada and Beck) cloud her judgement and heavily paid the price for it. The wound has hardly healed and she’s not willing to be hurt once more, nor is she willing to let somebody else be hurt in the process.
I do not think it was a coincidence in the writing/directing because it’s such a simple line and subtle use of the lighting, but it’s so very telling of her character.