if she were awake, she’d react and she’d remember in another interaction.
Plus you can trigger that scene as early as the beginning of the game, which you can’t do for the one actual awake scene on the toilet, because if she catches you peeking at the beginning, she panics and ends the scene.
She has to be at high lust to carry out the toilet scene, so the scene where she’s bent over the counter has her asleep.