Had the question about how she knew Anakin not been such a significant one, Padmé likely would have taken great humor at the boy's insistance that he was famous. Of course, it was significant, as was the answer, and it wasn't one she was intending to offer. That was Anakin's responsibility.
Turning her head to glance at her husband, meeting his gaze clear into the kitchen, she sent a wave of reassurance to him and smiled in the same fashion before looking down to the small boy just as Anakin, at long last, told him the truth. She, of course, had no way of knowing that her husband had said those very same words to their son before. She did, however, have a feeling that this Luke wasn't going to be nearly as upset as the other had likely been at such a statement.
Still, she couldn't say for certain so, before she went into the bedroom in search of a shirt for him to change into (following a bath, of course, as he really was quite dirty), Padmé remained where she was and simply waited for his reaction.